Stats Ch 11

Which formula for calculating the lower bound of a confidence interval is correct? a. -t(sdifference) + (MX - MY)sample b. t(smean) + (MX - MY)population c. t(sdifference) + (MX - MY)sample d. -t(smean) + (MX - MY)population

a. -t(sdifference) + (MX - MY)sample

In a(n) _____, one sample is used to compare a distribution of means during hypothesis testing. a. single-sample t test b. z test c. independent-samples t test d. dependent-samples t test

a. single-sample t test

The results of an independent-samples t test were t(18) = -2.11, p < 0.05. In this example, the degrees of freedom are: a. 18. b. 17. c. 0.05. d. -2.11.

a. 18.

The results of an independent-samples t test were t(18) = -2.11, p < 0.05. In this example, the sample size is: a. 0.05. b. 18. c. 20. d. -2.11.

c. 20.

The statement "On average, older adults have the same response time as younger adults" is an example of: a. effect size. b. statistical significance. c. the null hypothesis. d. the research hypothesis.

c. the null hypothesis.

Checking an independent-samples t test for the assumption of normality is part of step _____ of the six steps. a. 1 b. 2 c. 3 d. 4

a. 1

To calculate effect size for an independent-samples t test, use: a. Cohen's d. b. sample size. c. z score. d. standard deviation scores.

a. Cohen's d.

A study found statistically significant results for a hypothesis tested with an independent-samples t test. The author of the study reported her effect size for the test as 0.28. According to Cohen's convention, this effect size is considered: a. small. b. medium. c. large. d. to have no overlap.

a. small.

The results of an independent-samples t-test were t(18) = -2.11, p < 0.05. These results are: a. statistically significant. b. generalizable. c. meaningful. d. not statistically significant.

a. statistically significant.

Squared standard deviation is equivalent to the: a. standard error. b. variance. c. pooled variance. d. z test.

b. variance.

There is (are) _____ degree(s) of freedom calculations for an independent samples t-test. a. 0 b. 1 c. 3 d. 4

c. 3

A p level of 0.05 corresponds to a confidence interval of _____ percent. a. 68 b. 90 c. 95 d. 99.9

c. 95

Dr. Jameson wanted to know if IQ scores differed between male and female participants in his study. He gave 28 participants an IQ test and then compared IQ scores for gender differences. He hypothesized that there would be a statistically significant gender difference in IQ scores. Contrary to Dr. Jameson's hypothesis, there were no differences in IQ scores between men and women in his study. What is the dependent variable in this study? a. IQ scores b. sample size of 28 c. gender d. participants

a. IQ scores

Which example best illustrates APA's standards for reporting descriptive statistics for an independent-samples t test? a. On average, men scored significantly lower (M = 4.33, SD = 0.22) compared to women (M = 6.59, SD = 0.19) on reaction time. b. On average, men scored significantly lower (μ = 4.33, s = 0.22) compared to women (μ = 6.59, s = 0.19) on reaction time. c. On average, men scored significantly lower compared to women (M = 4.33, SD = 0.22 versus M = 6.59, SD = 0.19) on reaction time. d. On average, men scored significantly lower (X = 4.33, SD = 0.22) compared to women (X = 6.59, SD = 0.19) on reaction time.

a. On average, men scored significantly lower (M = 4.33, SD = 0.22) compared to women (M = 6.59, SD = 0.19) on reaction time.

_____ is a weighted average of the two estimates of _____. a. Pooled variance; variance b. Variance; pooled variance c. Pooled variance; standard deviation d. Standard deviation; pooled variance

a. Pooled variance; variance

Researchers were interested in whether relaxation training decreases the number of headaches a person experiences. They randomly assigned 20 participants to a control group (no relaxation training) or a relaxation training group and noted the change in number of headaches each group reported from the week before training to the week after training. The independent variable in this study is: a. training type. b. number of headaches. c. control group. d. relaxation training.

a. training type.

In order to report the exact p value associated with the test statistic for an independent-samples t test, we need to: a. use software to obtain the value. b. record the value from the t table under the 0.05 p level. c. compute Cohen's d. d. record the value from the t table under the 0.01 p level.

a. use software to obtain the value.

The two data transformation options discussed in the chapter are: a. logarithmic and square root transformations. b. converting scale data to ordinal data and square root transformation. c. scale data transformation and ordinal conversion. d. skew transformation and parametric test conversion.

b. converting scale data to ordinal data and square root transformation.

The formula for the total degrees of freedom for the independent-samples t test is: a. N. b. dfX + dfY. c. N - 1. d. (N - 1)(N - 1).

b. dfX + dfY.

s 2 pooled is the symbol for: a. variance. b. pooled variance. c. standard deviation. d. pooled mean.

b. pooled variance.

Dr. Jameson wanted to know if IQ scores differed between male and female participants in his study. He gave 28 participants an IQ test and then compared IQ scores for gender differences. He hypothesized that there would be a statistically significant gender difference in IQ scores. Contrary to Dr. Jameson's hypothesis, there were no differences in IQ scores between men and women in his study. Based on the information provided, does this study meet the assumption of normality? Why or why not? a. Yes; it is normally distributed because the sample size is large. b. No; it is not normally distributed because the small sample size is small. c. We do not know whether it is normally distributed and the sample size is not at least 30 participants. d. Yes; the population is likely to be normally distributed because the sample size is less than 30.

c. We do not know whether it is normally distributed and the sample size is not at least 30 participants.

When calculating effect size for an independent-samples t test, _____ sample size. a. add b. divide by c. disregard d. multiply by

c. disregard

Unnithan, Houser, and Fernhall (2006) were interested in whether playing the game Dance Dance Revolution (DDR) affected the heart rate of overweight and non-overweight adolescents differently. A group of 22 adolescents, 10 classified as overweight and 12 as not overweight played DDR for 12 minutes, during which time the researchers measured each participant's heart rate. Which statistical test should the researchers use to analyze their data? a. single-sample t test b. z test c. independent-samples t test d. dependent-samples t test

c. independent-samples t test

The appropriate hypothesis test to use for a between-groups design with two groups is a(n): a. z test. b. paired-samples t test. c. independent-samples t test. d. single-sample t test.

c. independent-samples t test.

A study found statistically significant results for a hypothesis tested with an independent-samples t test. The author of the study reported her effect size for the test as 0.82. According to Cohen's convention, this effect size is considered: a. small. b. medium. c. large. d. to have no overlap.

c. large.

Which formula for calculating the upper bound of a confidence interval is correct?

c. t( sdifference) + ( MX - MY) sample

Which of these illustrates a statistically insignificant result for an independent-samples t test? a. t(N - 1) = 2.33, p < 0.05 b. t(19) = 2.33, p < 0.05 c. t(19) = 2.33, p > 0.05 d. t(N - 2) = 2.33, p < 0.05

c. t(19) = 2.33, p > 0.05

When statisticians describe pooling the variances, they mean: a. adding the standard deviations of the two samples. b. adding the variances of the two samples. c. taking the average of the two variances, accounting for sample size. d. taking the average of the two variances, disregarding sample size.

c. taking the average of the two variances, accounting for sample size.

A study found statistically significant results for a hypothesis tested with an independent-samples t test. The author of the study reported her effect size for the test as 0.53. What is true of the two sample means? a. The two sample means overlap 53 percent. b. The two samples likely come from the same distribution. c. The two sample means do not indicate meaningful differences between groups. d. The two sample means are 0.53 standard deviations apart.

d. The two sample means are 0.53 standard deviations apart.

A study found statistically significant results for a hypothesis tested with an independent-samples t test. The author of the study reported her effect size for the test as 1.24. What is true of the two sample means? a. The two sample means overlap 85 percent. b. The two samples likely come from the same distribution. c. The two sample means do not indicate meaningful differences between groups. d. The two sample means are 1.24 standard deviations apart.

d. The two sample means are 1.24 standard deviations apart.

The fourth step in calculating a confidence interval for an independent-samples t test is to: a. look up the t statistics for the lower and upper bounds. b. draw a normal curve. c. write the percentages for the upper and lower bounds. d. convert the t statistics to raw differences between means.

d. convert the t statistics to raw differences between means.

The formula Sdifference = √(s^2difference) is used to calculate the: a. pooled variance estimate. b. standard deviation for an independent-samples t test. c. squared standard error. d. estimated standard error of the distribution of mean differences.

d. estimated standard error of the distribution of mean differences.

A clinical researcher was interested in determining whether her interventions for depression were effective in minimizing depression symptoms among her participants. To assess the effectiveness of her treatment program, she administered a depression inventory prior to treatment and after treatment. She hypothesized that depression scores would be lower at time two compared to time one. She then compared the mean differences between the two groups and found that her treatment was effective. Which statistical test was the researcher MOST likely to have used to test her hypothesis? a. single-sample t test b. z test c. independent-samples t test d. paired-samples t test

d. paired-samples t test

The mean of the comparison distribution for the null hypothesis of an independent-samples t test is: a. always 0. b. sometimes 0. c. always 1. d. sometimes 1.

a. always 0.

If two sample means come from the exact same distribution, then the distribution of differences between means against which they will be compared should have a mean of: a. 2. b. 1. c. 0. d. -1.

c. 0.

In an independent-samples t test, how is the research hypothesis symbolized? a. H1: μ1 ≠ μ2 b. H0: μ1 ≠ μ2 c. H1: μ1 = μ2 d. H0: μ1 = μ2

a. H1: μ1 ≠ μ2

Why is it necessary to use the pooled variance when conducting an independent-samples t test? a. We are working with two samples and an estimate of spread based on two samples is likely to be more accurate than an estimate of spread based on a single sample. b. It is necessary to estimate the standard deviation of the two samples in order to compare the two samples to one another. c. Estimating the spread of the sample using the standard deviation increases the generalizability of results. d. Using the pooled variance helps the researcher identify skewness.

a. We are working with two samples and an estimate of spread based on two samples is likely to be more accurate than an estimate of spread based on a single sample.

Data transformations can be useful when there is: a. a small sample and the data suggest the presence of skew. b. data that do not represent the desired results adequately. c. ordinal data and you want to perform parametric tests. d. unequal N in the groups.

a. a small sample and the data suggest the presence of skew.

To calculate a confidence interval for an independent-samples t test, use the: a. difference between means. b. difference between medians. c. mean of the first group only. d. mean of the second group only.

a. difference between means.

The comparison distribution for an independent-samples t test is a distribution of: a. differences between means. b. means. c. mean of difference of scores. d. scores.

a. differences between means.

Dr. Jameson wanted to know if IQ scores differed between male and female participants in his study. He gave 28 participants an IQ test and then compared IQ scores for gender differences. He hypothesized that there would be a statistically significant gender difference in IQ scores. Contrary to Dr. Jameson's hypothesis, there were no differences in IQ scores between men and women in his study. From the results of the study, Dr. Jameson must _____ the null hypothesis and _____ the research hypothesis. a. fail to reject; reject b. reject; fail to reject c. retest; reject d. reject; retest

a. fail to reject; reject

The first step in calculating a confidence interval for an independent-samples t test is to: a. look up the t statistics for the lower and upper bounds. b. draw a normal curve. c. write the percentages for the upper and lower bounds. d. convert the t statistics to raw score differences between means.

b. draw a normal curve.

In addition to reporting the results of statistical hypothesis testing, it is also recommended that researchers report: a. confidence intervals and random selection results. b. effect size and confidence intervals. c. effect size and median differences. d. effect size and mean difference scores.

b. effect size and confidence intervals.

A study found statistically significant results for a hypothesis tested with an independent-samples t test. The author of the study reported her effect size for the test as 0.53. According to Cohen's convention, this effect size is considered: a. small. b. medium. c. large. d. to have no overlap.

b. medium.

Researchers were interested in whether relaxation training decreases the number of headaches a person experiences. They randomly assigned 20 participants to a control group or a relaxation training group and noted the change in number of headaches each group reported from the week before training to the week after training. The dependent variable in this study is: a. training type. b. number of headaches. c. control group. d. relaxation training.

b. number of headaches.

In an independent-samples t test, the _____ is used rather than the _____. a. standard deviation; pooled variance b. pooled variance; standard deviation c. standard deviation; variance d. variance; pooled variance

b. pooled variance; standard deviation

Which of these illustrates the APA format for reporting statistically significant results for an independent-samples t test? a. t(N - 1) = 2.33, p < 0.05 b. t(19) = 2.33, p < 0.05 c. t(19) = 2.33, p > 0.05 d. t(N - 2) = 2.33, p < 0.05

b. t(19) = 2.33, p < 0.05

Mehl (2007) published in the journal Science the results of an extensive study of 396 men and women, comparing the number of words uttered per day by each sex. Is the population likely to be normally distributed? Why or why not? a. Yes; the population is likely to be normally distributed because the sample size is greater than 200. b. No; the population is not likely to be normally distributed because it has a small sample size. c. Yes; the population is likely to be normally distributed because the sample is greater than 30. d. We do not know whether the population is normally distributed because we do not have information on the population.

c. Yes; the population is likely to be normally distributed because the sample is greater than 30

The square root transformation offers an advantage over converting data to an ordinal scale because it: a. addresses skew. b. helps to address concerns associated with small samples. c. allows for the use of parametric tests. d. retains the original separation between data points.

c. allows for the use of parametric tests.

Dr. Jameson wanted to know if IQ scores differed between male and female participants in his study. He gave 28 participants an IQ test and then compared IQ scores for gender differences. He hypothesized that there would be a statistically significant gender difference in IQ scores. Contrary to Dr. Jameson's hypothesis, there were no differences in IQ scores between men and women in his study. What is the independent variable in this study? a. IQ scores b. sample size of 28 c. gender d. participants

c. gender

A psychologist is interested in whether working memory is influenced by sleep loss. The psychologist administers a measure of working memory to two groups of subjects. The subjects in one group were kept awake for the entire night and the subjects in the other group maintained their normal sleep schedules. Which statistical analysis should be performed to answer the question "Does sleep loss affect working memory?" a. single-sample t test b. z test c. independent-samples t test d. paired-samples t test

c. independent-samples t test

Dr. Jameson wanted to know if IQ scores differed between male and female participants in his study. He gave 28 participants an IQ test and then compared IQ scores for gender differences. He hypothesized that there would be a statistically significant gender difference in IQ scores. Contrary to Dr. Jameson's hypothesis, there were no differences in IQ scores between men and women in his study. Which test was Dr. Jameson MOST likely to use to test his hypothesis? a. paired-samples t test b. z test c. independent-samples t test d. single-samples t test

c. independent-samples t test

In a(n) _____, each participant is assigned to only one group in order to compare mean differences in a between-groups design. a. single-sample t test b. z test c. independent-samples t test d. dependent-samples t test

c. independent-samples t test

In a(n) _____, each participant is assigned to only one group in order to compare mean differences. a. single-sample t test b. z test c. independent-samples t test d. dependent-samples t test

c. independent-samples t test

Mehl (2007) published in the journal Science the results of an extensive study of 396 men and women comparing the number of words uttered per day by each sex. Which statistical test should Mehl use to analyze the data? a. single-sample t test b. z test c. independent-samples t test d. dependent-samples t test

c. independent-samples t test

Researchers were interested in whether relaxation training decreases the number of headaches a person experiences. They randomly assigned 20 participants to a control group or a relaxation training group and noted the change in number of headaches each group reported from the week before training to the week after training. Which statistical analysis should be performed to answer the researchers' question? a. single-sample t test b. z test c. independent-samples t test d. dependent-samples t test

c. independent-samples t test

There are three steps involved in creating the comparison distribution for the independent-samples t test, and those steps are repeated many times. Which of these is the sequence described in the text? a. randomly select a pair of scores, subtract the second score from the first, and record the difference between scores b. randomly select a group of scores, calculate their mean, and plot that mean on a distribution c. randomly select scores and calculate their mean as the group 1 mean, randomly select another group of scores and calculate their mean as the group 2 mean, and subtract the second mean from the first. d. randomly select a score, subtract the mean from the score, and plot the difference

c. randomly select scores and calculate their mean as the group 1 mean, randomly select another group of scores and calculate their mean as the group 2 mean, and subtract the second mean from the first.

In an independent-samples t test, how is the null hypothesis symbolized? a. H1: μ1 ≠ μ2 b. H0: μ1 ≠ μ2 c. H1: μ1 = μ2 d. H0: μ1 = μ2

d. H0: μ1 = μ2

In a(n) _____, a within-groups design with two groups is used to compare the distribution of mean difference scores. a. single-sample t test b. z test c. independent-samples t test d. paired-samples t test

d. paired-samples t test

The statement "On average, older adults have a different response time than younger adults" is an example of: a. effect size. b. statistical significance. c. the null hypothesis. d. the research hypothesis.

d. the research hypothesis.

To determine the critical values or cutoffs for an independent-samples t test, use: a. degrees of freedom for group 1. b. degrees of freedom for group 2. c. N - 1. d. total degrees of freedom.

d. total degrees of freedom.