Stats Exam #3

True or False: A researcher reports the following result for a blower-tail critical test at a 0.05 level of significance, t(40)= 3.212, and accurately concludes that this result is significant.

False

In hypothesis testing, a researcher's decision: a. is based on a probability b. depends on the level of significance for a hypothesis test c. can be to retain or reject the null hypothesis d. all of the above

d. all of the above

True or False: A researcher must know the population variance in order to compute a t-test.

false

A researcher directly controls for the probability of a _______________, but does not directly control fro the probability of a ________________. a. type 1 error; alpha level b. type 2 error; beta level c. type 1 error; type 2 error d. type 2 error; type 1 error

type 1 error; type 2 error

T or F: The test statistic determines whether or not an effect exists in a population; effect size measures the size of an observed effect in a population.

true

True or False: A researcher computes a one-independent sample t-test and finds that the result is undefined (the denominator is equal to 0). This happens when the same score is recorded for all participants in a study.

true

A researcher records the number of distracters (such as noises) that preschool-aged children ignore while watching a popular Sunday morning cartoon show. Assuming that the population variance is unknown, what type of t-test is appropriate for this study? a. one-independent sample t-test b. two-independent sample t-test c. There is not enough information to answer this question.

a. one-independent sample t-test

The estimated standard error in the t-statistic uses the ________ to estimate the ________ when the population variance is unknown. a. sample variance; population variance b. population variance; sample variance c. standard error; sample variance d. degrees of freedom; sample size

a. sample variance; population variance

A researcher conducts two studies. Each study was a one-independent sample z-test. Both studies placed the rejection region in both tails and measured the same sample mean. The alpha level in Study 1 was larger than the alpha level used in Study 2. Which study i s associated with greater power to detect an effect? a. study 1 b. study 2 c. they are associated with the same level of power

a. study 1

A researcher computes a test statistic and finds that the p value for this test is 0.03. What does this result mean? a. there is a 3% likelihood of obtaining the test statistic value, if the null were true. b. the probability of committing a type 1 error if we retain the null hypothesis is 3%. c. the probability of committing a type 2 error if we reject the null hypothesis is 3%. d. there is a 3% likelihood that the researcher's hypothesis is correct.

a. there is a 3% likelihood of obtaining the test statistic value, if the null were true.

True or False: A researcher reports the following result for a two-tailed test at a 0.05 level of significance, t(24)=2.010, and correctly decides to reject the null hypothesis.

false

A researcher measures mean health scores of children at a local school and compares these scores to the mean health score known in the general population. Assuming that the population variance is unknown, what type of t-test is appropriate for this study? a. one-independent sample t-test b. two-independent sample t-test c. there is not enough information to answer this question

a. one-independent sample t-test

True or False: As the population standard deviation increases, the power to detect an effect increases.

False

A researcher reports that the size of an effect in Population A is d = 0.10 and the effect size in Population B is d = 0.34. Which population is associated with greater power to detect an effect? a. Population A b. Population B c. They are associated with the same level of power.

b. Population B

A researcher conducts two t-tests. Test 1 is a two-tailed test with a smaller sample size at a .05 level of significance. Test 2 is a two-tailed test with a larger sample size at a .05 level of significance. a. Test 1 is associated with larger degrees of freedom. b. Test 2 is associated with larger degrees of freedom. c. Each test is associated with the same degrees of freedom. d. It depends; there is not enough information to answer this question.

b. Test 2 is associated with larger degrees of freedom.

The probability of committing a Type I error is stated by ________; the probability for committing a Type II error is stated by ________. a. beta; alpha b. alpha; beta c. a p value; a t value d. the complement of the power; the power

b. alpha; beta

The ________ is an inferential statistic used to determine the number of standard deviations in a t-distribution that a sample mean deviates from the mean value or mean difference stated in the null hypothesis. a. t-distribution b. t-statistic c. standard error d. degrees of freedom

b. t-statistic

Given the following values: μ = 10, M = 8, σμ = 0.5, conduct a one-independent sample z-test at a .05 level of significance. What is the decision for a two-tailed test? a. to reject the null hypothesis b .to retain the null hypothesis c. There is not enough information since the sample size is not given.

a to reject the null hypothesis

Given the following values: m = 10, M = 8, sm = 0.5, conduct a one-independent sample z-test at a .05 level of significance. What is the decision for a two-tailed test? a) to reject the null hypothesis b) to retain the null hypothesis c) There is not enough information since the sample size is not given.

a) to reject the null hypothesis

The first step to hypothesis testing requires that a researcher: a. states the hypothesis b. make a decision c. compute a test statistic d. conduct a study

a. states the hypothesis

Which of the following statements regarding the null hypothesis is true? a. the null hypothesis always makes statements about a population parameter. b. a decision in hypothesis testing in made about the alternative hypothesis, not the null hypothesis. c. the null hypothesis is the only hypothesis stated in hypothesis testing. d. all of the above

a. the null hypothesis always makes statements about a population parameter.

A researcher obtains z = 2.04 for a one-independent sample z-test. What is the decision for this test at a .05 level of significance? (assume there is no type III error) a. to reject the null hypothesis b. to retain the null hypothesis c. It depends on whether the test is one-tailed or two-tailed. d. There is not enough information to make a decision.

a. to reject the null hypothesis

Based on the effect size conventions, d = 0.60 is a: a) small effect size b) medium effect size c) large effect size

b) medium effect size

Given the following values: m = 6.0, M = 7.6, n= 36, s = 6, conduct a one-independent sample z-test at a .05 level of significance. For a one-tailed test, upper-tail critical, what is the decision? a) to reject the null hypothesis b) to retain the null hypothesis c) there is not enough information since the sample size is not given.

b) to retain the null hypothesis

Given the following values: m = 6.0, M = 7.6, n= 36, s = 6, conduct a one-independent sample z-test at a .05 level of significance. For a one-tailed test, upper-tail critical, what is the decision? a) to reject the nullhypothesis b) to retain the null hypothesis c) there is not enough information since the sample size is not given.

b) to retain the null hypothesis

A key difference between a t-statistic and a z-statistic is that the standard error is ______________ to compute a t-statistic. a. removed b. replaced c. estimated d. placed in the numerator

c. estimated

Based on the effect size conventions, d=0.99 is a: a. small effect size b. medium effect size c. large effect size

c. large effect size

A professor gives an exam in which the mean score is 78 points. She gives another exam to test whether or not scores change. In this example, the null hypothesis is a. μ ≠ 78 b. M ≠ 78 c. m = 78 d. M = 78

c. m=78

When a researcher decides to retain the null hypothesis because the rejection region was located in the wrong tail, this is called: a. type 1 error b. type 2 error c. type 3 error d. correct decision

c. type 3 error

Given the following values: m= 6.0, M = 7.6, n= 36, σ= 6, conduct a one-independent sample z-test at a .05 level of significance. For a one-tailed test, upper-tail critical, what is the decision? a. to reject the null hypothesis b. to retain the null hypothesis c. There is not enough information since the sample size is not given.

b. to retain the null hypothesis

The ________ is an inferential statistic used to determine the number of standard deviations in a z-distribution that a sample mean deviates from the mean value or mean difference stated in the null hypothesis. a. t-distribution b. z-statistic c. standard error d. degrees of freedom

b. z-statistic

A researcher selects a sample of 32 participants who are assigned to participate in a study with one group. What are the degrees of freedom for this test? a. 32 b. 30 c. 31 d. there is not enough information to answer this question

c. 31

Researchers state a level of significance in terms of an alpha level. The alpha level indicates: a. the probability of committing a type 1 error b. the probability of incorrectly rejecting the null hypothesis c. the probability value for the rejection region d. all of the above

d. all of the above

The t-distribution is similar to the z-distribution except: a. it is associated with greater variability b. it is characterized by "thicker" tails compared with the z-distribution c. it is associated with scores being more likely in the tails of the distribution d. all of the above

d. all of the above

________ allows researchers to describe (1) how far mean scores have shifted in the population, or (2) the percentage of variance that can be explained by a given variable. a. significance b. probability c. power d. effect size

d. effect size

A researcher reports that the size of an effect in some population is d = 0.88. Which of the following is an appropriate interpretation for d? a) The effect observed in the population was significant. b) Mean scores were significant by 0.88 points in the sample. c) Mean scores were significant by 0.88 points in the population. d) Mean scores shifted 0.88 standard deviations in the population.

Not A

A researcher reports a significance effect in some population. If he computes both an eta-squared and an omega-squared effect size estimate, then which estimate will be the largest? a. eta-squared b. omega-squared c. it depends on the sample size d. it depends on the value of the t-statistic

a. eta-squared

In step 2 of hypothesis testing, researchers state a level of significance to minimize the probability of: a. rejecting a true null hypothesis b. retaining a false null hypothesis c. inflating the power of a decision d. all of the above

a. rejecting a true null hypothesis

True or False: If d=0.28, then we conclude that mean scores in some population have shifted 0.28 standard deviations below the mean.

False

A researcher records the number of distracters (such as noises) that preschool-aged children ignore while watching a popular Sunday morning cartoon show. What can she do to obtain conclusive evidence for this problem? a. obtain a random sample of representative children b. collect data that allows enumerating distractors c. use inferential statistics using the data that are gathered d. do all of the above

d. do all of the above

A researcher reports that the size of an effect in some population is d=0.88. Which of the following is an appropriate interpretation for d? a. the effect observed in the population was significant b. mean scores were significant by 0.88 points in the sample c. mean scores were significant by 0.88 points in the population d. mean scores shifted 0.88 standard deviations in the population

d. mean scores shifted 0.88 standard deviations in the population