# A Comprehensive Guide to Z-Test: Questions and Answers PDF

The Z-test is a statistical hypothesis test used to determine whether the means of two data sets differ significantly. It is a powerful tool in data analysis and research.

In this comprehensive guide, we will explore common questions related to the Z-test and provide detailed answers. Whether you are a student, researcher, or data analyst, this guide will enhance your understanding of the Z-test and its applications.

## Understanding the Z-Test and Its Purpose

The Z-test is a parametric statistical test used to compare sample means to a known population mean. It helps determine if there is a significant difference between the two means.

## The Difference Between Z-Test and T-Test

While both the Z-test and the T-test compare means, they differ in their applications. The Z-test is suitable for large sample sizes, while the T-test is used when sample sizes are small.

## When to Use a Z-Test in Statistical Analysis

The Z-test is appropriate when the population standard deviation is known or when the sample size is large enough to assume the normal distribution.

## Calculating Z-Scores and P-Values

Z-scores represent the number of standard deviations a data point is from the mean. P-values indicate the probability of obtaining the observed results by chance.

## Interpreting Z-Test Results

Interpreting Z-test results involves comparing the calculated Z-value to critical values or using p-values to determine statistical significance.

## One-Tailed vs. Two-Tailed Z-Tests

A one-tailed Z-test is used when the research hypothesis specifies the direction of the difference, while a two-tailed Z-test is used when the direction is not specified.

## Assumptions of the Z-Test

The Z-test assumes that the data is normally distributed, the samples are independent, and the sample size is sufficiently large.

## Advantages and Limitations of the Z-Test

The Z-test offers simplicity, efficiency, and applicability to large samples. However, it may not be suitable for small samples or non-normally distributed data.

## Z-Test Applications in Real-World Scenarios

The Z-test finds applications in various fields, such as medicine, economics, and social sciences. It is used to compare means in clinical trials, marketing research, and opinion polls.

## Z-Test Questions

• We ask if the attitudes toward fuel costs of 100 owners of hybrid electric cars (X = 76) are different from those on a national survey of owners of non-hybrid cars (mu = 65, X = 24). Higher scores indicate a more positive attitude. (a) Is this a one-or tw
• We ask if the attitudes toward fuel costs of 100 owners of hybrid electric cars (X=76) are different from those on a national survey of owners of non-hybrid cars (uï¿½=65, ox=24) . Higher scores indicat
• A study by Edmunds.com examined the time it takes for owners of hybrid vehicles to recoup their additional cost through reduced fuel consumption. Suppose that a random sample of 9 hybrid cars showed a
• The Toyota Prius uses both gasoline and electric power. Toyota claims its mileage per gallon is 52. A random sample of 40 cars is taken, and each sampled car is tested for its fuel efficiency. Assuming that 52 miles per gallon is the population mean and 2
• According to the Deloitte EV Survey, 5 % of respondents indicated that they would be willing to pay an extra $500 or more for an electric vehicle versus one with a gasoline engine. A random sample of 25 adults have been selected. Use the Poisson dist • A study of 300 recent new car purchasers yielded the following results when asked the question. Yes = 156 No =144 (a) Find a point estimate for the population percentage of all new car purchasers that think the quality of Japanese cars is better than Am • In a recent consumer survey, 87 out of 300 randomly selected SUV owners stated they are dissatisfied with the performance of their vehicle. Find a 95% confidence interval for the proportion of all SUV owners who are dissatisfied w/ their vehicle performan • A recent survey of gasoline prices indicated that the national average was$4.098 per gallon. The Dallas Automobile Club claimed that gasoline in Texas was significantly lower than the national average. A survey covering 10 different suburbs in Dallas fou
• Solar energy is considered by many to be the energy of the future. A recent survey was taken to compare the cost of solar energy to the cost of gas or electric energy. The result of the survey reveale
• Solar energy is considered by many to be the energy of the future. A recent survey was taken to compare the cost of solar energy to the cost of gas/electric energy. Results of the survey revealed that
• A recent gasoline survey said that the national average price of gasoline was $1.498 a gallon. It was felt that gasoline in Texas was significantly lower than the national average. A survey of 10 diff • A recent survey was conducted to compare the cost of solar energy to the cost of gas or electric energy. Results of the survey revealed that the distribution of the amount of the monthly utility bill • A survey of a random sample of 100 adults was taken. Their personality type (A or B) and their attitude toward small cars (positive, neutral, negative) were recorded. 1. The researcher is interested i • Solar energy is considered by many to be the energy of the future. A recent survey was taken to compare the cost of solar energy to the cost of gas or electric energy. Results of the survey revealed that the distribution of the amount of the monthly utili • New car owners were asked to evaluate their experiences in buying a new car during the past 12 months. In the survey, the owners indicated they were most satisfied with their experiences at the follow • A recent gasoline survey said that the national average price of gasoline was$1.498 per gallon. It was felt that the gasoline in Texas was significantly lower than the national average. A survey of 10 different suburbs in Dallas, Texas found the average
• A survey was conducted to determine the difference in gasoline mileage for two truck models. A random sample was taken for each model of truck, and the mean gasoline mileage, in miles per gallon, was
• A recent gasoline survey said that the national average price of gasoline was $1.498 a gallon. It was felt that gasoline in Texas was significantly lower than the national average. A survey of 10 different suburbs in Dallas, Texas found the average price • A manufacturer claims that a particular automobile model will get 50 miles per gallon on the highway. The researchers at a consumer-oriented magazine believe that this claim is high and plan a test with a simple random sample of 30 cars. Assuming the stan • A recent comprehensive survey found that 71.4% of the national population owns two cars. In a random sample of 150 heads of households in a certain community, 111 responded that they owned two cars. At alpha = 0.05, does this sample data indicate a differ • A survey was taken to see if there is a relationship between political affiliation and attitudes toward an environmental issue that will be on an upcoming ballot. Test at the .05 significance level. Response: What is x^2 _calculated (Chi-Squared calculate • A survey of 180 motorists revealed that they were spending on average$287 per year on car maintenance, with a standard deviation of $94. Construct 95% and 99% confidence intervals. How would you view the hypothesis that this spending was really about$30
• According to a poll on consumer behavior, 36% of people say they will only consider cars manufactured in their country when purchasing a new car. Suppose you select a random sample of 100 respondents.
• Suppose a study reports that the average price for a gallon of self-serve regular unleaded gasoline is $3.16. You believe that the figure is higher in your area of the country. You decide to test this • A marketing research survey shows that approximately 80% of the car owners surveyed indicated that their next car purchase will be either a compact or economy car. Assume the 80% figure is correct and five prospective buyers are interviewed. a. Find the p • A fuel-economy study was conducted for two Japanese automobiles, Honda and Toyota. One vehicle of brand was selected, and the mileage performance was observed for 11 and 9 tanks of fuel in each car respectively. The data are as follows (in MPG). Assume th • Do heavier cars use more gasoline? To answer this question, a researcher randomly selected 15 cars. He collected their weight (in hundreds of pounds) and the mileage (MPG) for each car. From a scatter • A survey was taken to see if there is a relationship between political affiliation and attitudes toward an environmental issue that will be on an upcoming ballot. Test at the .05 significance level. Response: State the research hypothesis. • A survey is conducted to determine whether the age of car and type of the car influences the annual maintenance cost. A sample of 10 cars is selected and the data is shown below. You want to detect if there are any outliers in the variable (“Age of car (m • A survey was taken to see if there is a relationship between political affiliation and attitudes toward an environmental issue that will be on an upcoming ballot. Test at the .05 significance level. Response: State the null hypothesis. • A survey was taken to see if there is a relationship between political affiliation and attitudes toward an environmental issue that will be on an upcoming ballot. Test at the .05 significance level. Response: Should you reject/accept the null hypothesis? • In a sample of 30 people, 18 indicated that they prefer domestic automobiles, 10 said they prefer foreign-made cars, 2 indicated no difference in their preference, At a 0.05 level of significance, de • A survey was taken to see if there is a relationship between political affiliation and attitudes toward an environmental issue that will be on an upcoming ballot. Test at the .05 significance level. Response: What is x^2 _critical at the .05 significance • According to a survey, 18% of the car owners said that they get the maintenance service done on their cars according to the schedule recommended by the auto company. Assume that this result is true for the current population of car owners. Answer the foll • Suppose a study reports that the average price for a gallon of self-serve regular unleaded gasoline is$3.16. You believe that the figure is higher in your area of the country. You decide to test this claim for your part of the United States by randomly c
• Suppose a study reports that the average price for a gallon of self-serve regular unleaded gasoline is $3.76. You believe that the figure is higher in your area of the country. You decide to test this claim for your part of the United States by randomly c • A sample of cars in 2010 and in 2020 was tested for their MPG. Below are the results. Below 17 18-25 Above 25 2010 30 45 12 2020 15 40 20 If one car is selected, find each probability: a.) P(below 17 mpg). b.) P(18-25 or 2020). c.) P(not 2020). d.) P(2010 • The Survey of Study Habits Attitudes (SSHA) is a psychological test that measures the motivation, attitude toward school, and study habits of students. Scores range from 0 to 200. The mean score for U.S. college students is about 115, and the standard de • A Fortune study found that the variance in the number of vehicles owned or leased by subscribers to Fortune magazine is 0.95. Assume a sample of 12 subscribers to another magazine provided the following data on the number of vehicles owned or leased: 2, 1 • The Fortune study found that the variance in the number of vehicles owned or leased by subscribers to Fortune magazine is 0.95. Assume a sample of 12 subscribers to another magazine provided the following data on the number of vehicles owned or leased: 2, • A research institute poll asked respondents if they acted to annoy a bad driver. In the poll, n = 2674, and x = 964 who said that they honked. Use a 99% confidence level. a. Find the best point estimate of the population proportion p? b. Identify the va • A recent survey of 1,000 US citizens found that 42% believe raising the maximum speed limit on highways will help the national productivity. Construct a 99% confidence interval for the true proportion of US citizens who believe this. • The accompanying data are from an article. Each of 309 people who purchased a Honda Civic was classified according to gender and whether the car purchased had a hybrid engine or not. Assume that one of these 309 individuals is to be selected at random. F • A survey is conducted to determine whether the age of car influences the annual maintenance cost. A sample of 10 cars is selected and the data is shown below. a. Test whether each of the regression pa • The following data is from an article. Each of 309 people who purchased a Honda Civic was classified according to gender and whether the car purchased had a hybrid engine or not. Suppose one of these 309 individuals is to be selected at random. Find the • In a study you obtain the following data representing the aggressive tendencies of some football players: 40, 30, 39, 40, 41, 39, 31, 28, 33 (a) Researchers have found that in the population of non-football players, \mu is 30 (sigma _X = 5) Using both • In a sample of 120 people, 50 indicated that they prefer domestic automobiles, 60 said they prefer foreign-made cars, and 10 indicated no difference in their preference. At a 0.05 level of significance, determine if there is evidence of a significant diff • We measure the self-esteem scores of a sample of statistics students, reasoning that this course may lower their self-esteem relative to that of the typical college student ( mu = 55 and sigma X = 11.35). We obtain these scores: 44, 55, 39, 17, 27, 38, 36 • According to a poll, 36% of people say they will only consider cars manufactured in their country when purchasing a new car. If a random sample of 100 respondents are selected, the probability is 68% that the sample will be contained within what symmetric • According to a poll, 36% of people say they will only consider cars manufactured in their country when purchasing a new car. If a random sample of 100 respondents are selected, the probability is 70% that the sample will be contained within what symmetric • A survey of magazine subscribers showed that 40% rented a car during the past 12 months for business reasons, 30% rented a car for both business and personal reasons, 35% percent did not rent a car for either business or personal reasons. How many percent • Please do question (8.38) A sample survey is designed to estimate the proportion of sports utility vehicles being driven in PEI. A random sample of 500 registrations are selected from a PEI database, • The Pew Research Center recently polled n = 1048 U.S. drivers and found that 69% enjoyed driving their automobiles. (a) Construct a 95% confidence interval for the proportion of U.S. drivers who enjoy driving their automobiles. (b) How many U.S. drivers • The owner of a gasoline station wants to study gasoline purchasing habits of motorists at his station. He selects a random sample of 60 motorists during a certain week, with the following results: The amount purchased was a sample mean = 11.3 Gallons; S= • The accompanying data are from an article. Each of 309 people who purchased a Honda Civic was classified according to gender and whether the car purchased had a hybrid engine or not. Suppose one of these 309 individuals is to be selected at random. Find • A research institute poll asked respondents if they acted to annoy a bad driver. In the poll, n = 2574, and bar x = 970 who said that they honked. Use a 99% confidence level. A. Find the best point es • The average cost per day of owning a car in the United States is$7.62. A researcher claims that a college student’s average daily cost is different from the national average. A random sample of 40 college students had an average cost of $6.78 with a stan • Suppose the data shown below are the results of a survey to investigate gas prices. Ten service stations were selected randomly in two cities each and the figures represent the prices of a liter of unleaded regular gas on a given day. Use the F test to de • A study is being conducted on the effect of gas price on the number of miles driven in a given month. Residents in two cities, one on the east coast and one on the west coast are randomly selected and asked to complete a questionnaire on the type of car t • You are a researcher interested in addressing the question: Does smiling cause mood to rise? (i.e become more positive? Sketch between participants and matched participants designs that address this question and discuss the advantages and disadvantages of • In a random sample of 280 cars driven at sea level, 38 of them produced more than 10 g of particulate pollution per gallon of fuel consumed. In a random sample of 77 cars driven at a higher elevation, 18 of them produced more than 10 g of particulate poll • You have been hired by the Ford Motor Company to do market research, and you must estimate the percentage of household in which a vehicle is owned. How many households must you survey if you want to b • The owner of a petrol station wants to study fuel-purchasing habits of motorists at his station. A random sample of 60 motorists during a particular week gave the following results: Amount purchased: x-bar = 42.8 liters S = 10.3 liters. 9 motorists purch • A research institute poll asked respondents if they acted to annoy a bad driver. In the poll, n = 2517, and x = 1140 who said that they honked. Use a 99% confidence level. Find the best point estimate of the population proportion p. • If there is no relationship between personality type and their attitude toward small cars for the population of all such adults, how many Type A adults would you have expected to have a positive attitude toward small cars? a. 0 b. 2 c. 22 d. 22.2 e. 23 f. • An automotive manufacturer wants to know the proportion of new car buyers who prefer foreign cars over domestic. Suppose a sample of 675 new car buyers is drawn. Of those sampled, 270 preferred foreign over domestic cars. Using the data, construct the 90% • In 2016 Auto Reliability Survey, Consumer Reports asked subscribers to report their maintenance and repair costs. Most individuals are aware of the fact that the average annual repair cost for an automobile depends on the age of the automobile. A research • In its 2016 Auto Reliability Survey, Consumer Reports asked subscribers to report their maintenance and repair costs. Most individuals are aware of the fact that the average annual repair cost for an automobile depends on the age of the automobile. A rese • You have been hired by the Ford Motor Company to do market research, and you must estimate the percentage of households in which a vehicle is owned. How many households must you survey if you want to • A survey on British Social Attitudes asked respondents if they had ever boycotted goods for ethical reasons Statesman, January 28, 2008. The survey found that 34% of the respondents have boycotted goo • A sample of 2500 random Americans asking if they believe the economy has improved. 885 respond yes while the others respond no. a Find a point estimate for the proportion of Americans who believe the • A survey revealed the amount of pocket money held by each student in a sample of students. The amounts in dollars are: 5.50, 10.20, 3.15, 6.08, 4.85, 4.80, 4.70, 8.52, 7.90, 6.10, 3.50, 5.40, 7.10, 9.60, 6.24, and 4.28. Assume &sigma; = 2.00. What is the • What is the first big change that American drivers made due to higher gas prices? According to an Access America survey, 40% said that it was cutting recreational driving. However, 24% said that it w • The survey of study habits and attitudes is a psychological test tht measures the motivation attitude toward school and study habits of students scores range from 0-200. the mean score for U.S college • The owner of a gasoline station wants to study gasoline purchasing habits by motorists at his station. He selects a random sample of 60 motorists during a certain week with the following results: the • The owner of a gasoline station wants to study gasoline purchasing habits of motorists at his station. He selects a random sample of of 60 motorists during a certain week, with the following results: • What is the value of the test statistic? a. 100 b. 9.89 c. 50 d. 4.94 Recently, students in a marketing research class were interested in the driving behavior of students driving to school. Specifically, the marketing students were interested if excee • When 500 college students were surveyed, 30% said that they own their car. Construct a 95% confidence interval for the proportion of college students who say they own their cars. Explain your answer. • A research institute poll asked respondents if they acted to annoy a bad driver. In the poll, n = 2517 , x = 1109 who said that they honked. Use a 99 % confidence level. a) Find the best point • The owner of a petrol station wants to study diesel-purchasing habits of motorists at his station. He selects a random sample of 85 motorists during a certain week and obtains the following sample statistics. 1. With regard to the amount purchased, the s • An agency surveyed people worldwide, asking them, “Do you live in a household with more than one car?” Of the 1062 respondents surveyed in India, 395 said they live in a household with more than one car. In Canada, of the 871 respondents, 439 said they li • A survey revealed the amount of pocket money held by each student in a sample of students. The amounts in dollars are 5.50, 10.20, 3.15, 6.08, 4.85, 4.80, 4.70, 8.52, 7.90, 6.10, 3.50, 5.40, 7.10, 9.60, 6.20, 4.28. Assume &sigma; = 2.00. Find the 99% conf • According to PayScale survey of MBA graduates, those with one to four years of experience had an average salary of$60,550 in 2017. Treat the result of this survey of 4,000 MBA graduates as population data. Assume the standard deviation is sigma = $18,250 • An automotive manufacturer wants to know the proportion of new car buyers who prefer foreign cars over domestic. Step 1 of 2: Suppose a sample of 1046 new car buyers is drawn. Of those sampled, 355 p • A survey examines customers’ preferences in having a sunroof in their car. Sunroof (S) No Sunroof (S’) Woman (W) 800 650 1450 Man (M) 1500 300 1800 2300 950 3250 a) Compute the Marginal Probabilities • The Survey of Study Habits and Attitudes (SSHA) is a psychological test, administered to students, that measures attitude towards school. Scores range from 0 to 200. The mean score for U.S. college st • A study of 3 different groups of 8 employees (24 people total) were surveyed to determine their daily commuting mileage. The boss wants to test the claim that the commuting mileage is the same for eac • An environmental group at a local college is conducting independent tests to determine the distance a particular make of automobile will travel while consuming only 1 gallon of gas. A sample of five cars is tested and a mean of 28.2 miles is obtained. Ass • It has been claimed that 65% of homeowners would prefer to heat with electricity instead of gas. A study finds that 60% of 200 homeowners prefer electric heating to gas. In a two-tail test at the 0.05 • A nationwide sample of influential Liberals and Conservatives was asked as a part of a comprehensive survey whether they favored lowering environmental standards so that high-sulphur coal could be burned in coal-fired power plants. The results were: | |Li • If there is no relationship between personality type and their attitude toward small cars for the population of all such adults, what is the expected value of the test statistic? a. 0 b. 0.495 c. 1.405 d. 2 • Six hundred consumers were asked whether they would like to purchase a domestic or a foreign automobile. Their responses are given below. Develop a 95% confidence interval for the proportion of all consumers who prefer to purchase domestic automobiles. • One survey conducted by a major leasing company determined that the Lexus is the favorite luxury car for 25% of leases in Atlanta. Suppose a US car manufacturer conducts its own survey in an effort to determine if this figure is correct. Of the 384 leases • Wilson Researchers at Cleary University want to know the proportion of students who own cars to assess whether or not they need to pave an additional parking lot. A survey of 500 traditional students indicates that 95% own cars. a) What is the standard de • When 370 college students were surveyed, 155 said they own their car. Find a point estimate for p , the population proportion of students who own their cars. A. 0.295 B. 0.419 C. 0.581 D. 0.721 • 1. A survey is conducted by the American Automobile Association to investigate the daily expense of a family of four while on vacation. Suppose that a sample of 64 families of four vacationing at Niag • A random sample of 1,040 satellite radio subscribers were asked, “Do you have a satellite radio receiver in your car?” The survey found that 208 subscribers did, in fact, have a satellite receiver in their car. a. From the sample, calculate an estimate of • An owner of a gasoline station wants to study gasoline purchasing habits by motorists at his station. He selects a random sample of 60 motorists during a certain Week, with the following results: – The amount purchased was X=11.3 gallons, S=3.1 gallons. • The owner of a gasoline station wants to study gasoline purchasing habits by motorists at his station. He selects a random sample of 60 motorists during a certain Week, with the following results: – The amount purchased was X=11.3 gallons, S=3.1 gallons. • A survey was taken to see if there is a relationship between political affiliation and attitudes toward an environmental issue that will be on an upcoming ballot. Test at the .05 significance level. Response: What is df (degrees of freedom)? • H0: 16.69 vs. HA: > 16.69 What is the test statistic for sample of size 30, mean 13.99, and standard deviation 2.14? Enter the test statistic with 2 decimal places. • Find t_c for a 0.90 confidence level when the sample is 8. • Testing: H_o: p = 0.56 H_A: p \neq 0.56 The sample consists of 109 subjects, with 66 successes. Calculate the test statistic, rounded to 2 decimal places. • The board of a major credit card company requires that the mean wait time for customers when they call customer services is at most 3.00 minutes. To make sure that the mean wait time is not exceedi… • Discuss when it is appropriate to use a one-sample z-test. • You wish to test the following claim (H_a) at a significance level of alpha = 0.002. H_0: mu = 74.2 H_a: mu greater 74.2 You believe the population is normally distributed, but you do not know the… • A researcher wishes to see if the average number of sick days a worker takes per year is greater than 5. A random sample of 26 workers at a large department store had a mean of 5.2. The standard de… • A used car dealer says that the mean price of a five-year-old truck (in average condition) is at most$13,000. You suspect this claim is incorrect and find that a random sample of 33 similar trucks…
• Assuming that the samples below are matched and contain data from approximately normally distributed populations, test the claim that the population corresponding to the first sample has a higher m…
• In a survey, it was stated that Americans watch television on average four (4) hours per day. Using the data from a survey of 50 students of a certain college (see data below), conduct a hypothesis…
• What is a z-score, and what does it tell you? Is it useful? Why?
• For a repeated-measures study with a total of n = 24 participants, a sample mean difference score of MD = 4 is obtained. If the variance of the difference scores is s^2 = 216, the t statistic is t…
• According to a study, people who move from home to home frequently as children tend to have lower than average levels of well-being as adults. To further examine this relationship, a psychologist o…
• An automobile owner found that 20 years ago, 76% of Americans said that they would prefer to purchase an American automobile. He believes that the number is much greater than 76% today. He selected…
• Fathers had heart attacks. Suppose the mean fasting cholesterol of teenage boys in the United States is mu = 175 mg/dL with sigma = 50 mg/dL. An SRS of 39 boys whose fathers had a heart attac
• The average annual salary of 20 female hospital administrators is \$80,900. These administrators believe they make less than their male counterparts because of sex bias. Published results suggest th…
• Local government is worried that runoff from a corporate farm has caused water in a nearby stream to become acidic. The pH is used to measure the acidity/alkalinity of a substance. Pure water, for…
• Select the best response: the total area under a t-curve is equal to: (a). -1 (b). 0 (c).1.
• Calculate the z-test statistic for a hypothesis test in which the null hypothesis states that the population proportion, p, equals 0.11 if the following sample information is present. n = 100 x = 7
• Insulation workers: twenty-six cancer deaths were observed in a cohort of 556 insulation workers. Based on national statistics, a cohort of this size and age distribution was expected to experience…
Center for Disease Control estimates the data that about 36.4% of teenagers were overweight in 2008. The definition of overweight is a body mass index (BMI) of over 25. The percentage was very simi…
An adventure company runs two obstacle courses, Fundash and Coolsprint, with similar designs. Since Fundash was built on rougher terrain, the designer of the courses suspects that the mean completi…
An adventure company runs two obstacle courses, Fundash and Coolsprint, with similar designs. Since Fundash was built on rougher terrain, the designer of the courses suspects that the mean completi…
To test the quality of the work of a commercial laboratory, duplicate analyses of a purified benzoic acid (68.8% C, 4.953% H) sample was requested. It is assumed that the relative standard deviatio…
A student at a four-year college claims that mean enrollment at four-year colleges is higher than at two-year colleges in the United States. Two surveys are conducted. Of the 35 four-year colleges…
Perform Z-tests to determine statistical significance. Population Mean = 100, Standard Deviation = 15 Sample Mean = 105, Sample Size = 300 Standard Error Critical Value (p<.05) =1.96 z statistic…
A student at a four-year college claims that mean enrollment at four-year colleges is higher than at two-year colleges in the United States. Two surveys are conducted. Of the 35 four-year colleges…
The U.S. Center for Disease Control reports that in 1900, the mean life expectancy is 47.6 years for whites and 33 years for nonwhites. Suppose a survey of randomly selected death records for white…
How does a correlated groups t test have more statistical power in comparison to an independent groups t test?
Question: Test the claim about the population mean at the given level of significance using the given sample statistics. Claim: mu = 40 alpha = 0.03 sigma = 3.26. Sample statistics: xbar = 39.9, n…
The length of human pregnancies is approximately normal with mean = 266 days and standard deviation =16 days. What is the probability that a randomly selected pregnancy lasts less than 258 days?
A production filling operation has a historical standard deviation of 6 ounces. When in proper adjustment, the mean filling weight for the production process is 50 ounces. A quality control inspect…
After implementing the educational program on 10 participants, our sample’s score on the comparison distribution is t_9 = 1.223 (alpha = 0.01) and our effect size is Cohen’s d = 0.76. Interpret the…
A professional employee in a large corporation receives an average of mu equals 44.2 e-mails per day. Most of these e-mails are from other employees in the company. Because of the large number of e…
For what type of population distributions would you recommend using the t-test?
A factory that manufactures bolts is performing a quality control experiment. Each object should have a length of no more than 13 centimeters. The factory believes that the length of the bolts exce…
The mean of the population was zero, the mean of your sample was 1.3 and the standard deviation was 2.6. How many participants were used in this study?
For a population with a mean of 75 and a standard deviation of 12, what proportion of sample means of size n = 16 fall above 82?
What is the design of the study when we compute the z-test and t-test versus when we compute a correlation coefficient?

### What is the formula for calculating the Z-score?

The Z-score formula is (X – Î¼) / (Ïƒ / âˆšn), where X is the sample mean, Î¼ is the population mean, Ïƒ is the population standard deviation, and n is the sample size.

### How do I determine statistical significance in a Z-test?

Statistical significance is determined by comparing the calculated Z-value to critical values from the standard normal distribution table or using p-values. If the p-value is below the significance level (e.g., 0.05), the results are considered statistically significant.

### Can the Z-test be used for small sample sizes?

The Z-test is most reliable for large sample sizes (usually n > 30). For small samples, the T-test may be more appropriate.

### What is the difference between a null hypothesis and an alternative hypothesis in the Z-test?

The null hypothesis (H0) states that there is no significant difference between the sample mean and the population mean. The alternative hypothesis (H1) suggests that there is a significant difference.

### How do I interpret a negative Z-score?

A negative Z-score indicates that the data point is below the mean, while a positive Z-score indicates that it is above the mean.

### Can I use the Z-test for non-numerical data?

No, the Z-test is specifically designed for numerical data, particularly continuous data that follows a normal distribution.

## Conclusion

The Z-test is a fundamental statistical tool that plays a crucial role in hypothesis testing and data analysis. Understanding its principles, assumptions, and applications can greatly benefit researchers and analysts in drawing meaningful conclusions from their data. By confidently applying the Z-test, professionals can make informed decisions based on statistical evidence.