Exam #4

T or F: The degrees of freedom for the related samples t-test is the number of difference scores minus one.

True

A researcher reduces her level of confidence interval from 99% to 90%. What will happen to the precision of her estimate? a. The estimate will be more precise b. The estimate will be less precise c. The precision of her estimate will not change d. It depends on the size of the population

a. The estimate will be more precise

T or F: When the null hypothesis is outside the confidence interval, this indicates that it would likely be retained with hypothesis testing.

False

T or F: Both estimates of proportion of variance, n2 and w2, are computed the same for independent and related samples t-tests.

True

T or F: When testing a hypothesis with one or two groups selected from a population with an unknown variance, a t-test is appropriate.

True

True or False: When testing a hypothesis with one or two groups selected from a population with an unknown variance, a t-test is appropriate.

true

T or F: A t-distribution with infinite degrees of freedom is a z-distribution.

True

T or F: A t-statistic estimates the standard error by using the sample variance to approximate the population variance.

True

Computing a two-independent sample t-test is appropriate when a) different participants are assigned to each group b) the population variance is unknown c) participants are observed one time d) all of the above

d) all of the above

Which type of error is used to compute the confidence interval for one sample selected from a population of known variance? a. standard error b. estimated standard error c. estimated standard error for the difference d. estimated standard error for the difference scores

a. standard error

A researcher conducts a study in which the population variance of difference scores between two groups is unknown. What type of t-test is most appropriate for this study? a. one-independent sample t-test b. two-independent sample t-test c. related samples t-test d. there is not enough information to answer this question

c. related samples t-test

Which of the following is a measure of proportion of variance for a one-way between-subjects ANOVA? a. eta-squared b. omega-squared c. estimated Cohen's d d. both A and B

d. both A and B

A researcher reports that the mean difference in response time to an auditory versus a visual cue is 0.83 seconds, with a pooled sample variance equal to 2.45. What is the effect size for this test using estimated Cohen's d? a. d=0.53; medium effect size b. d=0.53; large effect size c. d=0.34; small effect size d. d=0.34; medium effect size

a. d=0.53; medium effect size

A researcher compares the height of male executives in the U.S. to the average height of males (67 inches). He determines that the average height of male executives is 70 inches (95% confidence interval (CI) 68-72). Based on this result , what would the decision have beed for a hypothesis test? a. reject the null hypothesis b. retain the null hypothesis c. there is not enough information to answer this question

a. reject the null hypothesis

A researcher asks a sample of brothers and sisters to rate how positive their family environment was during childhood. In this study, the differences in ratings between each brother and sister pair were compared. The type of design described here is called a: a. repeated measures design b. matched samples design c. both A and B

b. matched samples design

A lowercase k is used to denote: a. the number of groups in a study b. the number of participants in a study c. the number of levels of the factor in a study d. both A and C

d. both A and C

Which of the following is the denominator of the test statistic for the related samples t-test? a. standard error b. estimated standard error c. estimated standard error for the difference d. estimated standard error for difference scores

d. estimated standard error for difference scores

A researcher conducts a study using the one-way between-subjects ANOVA. He computes SSbg=120 and SSe=200. What is the effect size for this test using eta-squared? a. 0.60 b. 0.38 c. 1.67 d. there is not enough information to answer this question

b. 0.38

True or False: The estimated Cohen's d for the related samples t-test uses the sample standard deviation for difference scores as a estimate of the standard deviation of difference scores in the population.

true

True or False: There are two sources of variation in a one-way between-subjects ANOVA-- one attributed to differences between groups and one attributed to error.

true

The test statistic for a related sample t-test makes tests concerning a single sample of: a. raw scores b. difference scores c. participant scores d. original data

b. difference scores

All other things being equal, as the sample size increases, what happens to the critical value for a related samples t-test (or for any t-test, for that matter)? a. the critical value increases b. the critical value decreases c. the critical value does not change d. it depends on the value of the test statistic

b. the critical value decreases

True or False: The estimation formula for the one-independent sample t is M +- t(Smd)

true

True or False: When the proportion of variance explained by some treatment is larger than 0.25, we conclude that there is a large effect in the population.

true

In a sample of 26 participants, a researcher estimates the 90% CI for a sample with a mean of MD=0.6 and an estimated standard error for the difference scores of 0.1. What is the upper confidence limit for this interval? a. 0.77 b. -0.5 c. 1.7 d. 2.5

a. 0.77

Computing a one-way between subjects ANOVA is appropriate when: a. different participants are observed one time in each of two or more groups for one factor b. the same participants are observed in each of two or more groups for one factor c. the levels or one or more factors are manipulated d. all of the above

a. different participants are observed one time in each of two or more groups for one factor

A researcher reports the mean difference in the body weight of rats following a pharmacological versus control treatment is 14 grams, with a pooled sample variance equal to 256. What is the effect size for this test using estimated Cohen's d? a. d=0.06; small effect size b. d=0.08; small effect size b. d=0.88; large effect size d. There is not enough information to answer

b. d=0.88; large effect size

Each of the following is needed to computed estimated Cohen's d except: a. the mean difference b. the standard error c. the standard deviation of difference scores

b. the standard error

A researcher conducts a study measuring difference in brain activity among rats placed on either a continuous or intermittent reward schedule. 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. not enough information

b. two-independent sample t-test

T or F: A two-independent sample t-test is used when the same participants are observed in each of two groups.

False

T or F: As the degrees of freedom for a t-test increase, the critical values for that test also increase.

False

It is most appropriate to report effect size with a significant result. Why is it generally inappropriate to report effect size with insignificant results? a. because insignificant results will always have an effect size equal to 0. b. because insignificant results indicate that an effect size is also insignificant. c. because it makes little sense to report the size of an effect that you just concluded doesn't exist d. because the probability of the size of an effect varies depending on the significance of the result

a. because insignificant results will always have an effect size equal to 0.

Computing a two-independent sample t-test is appropriate when: a. difference participants are assigned to each group b. the population variance is unknown c. participants are observed one time d. all of the above

a. difference participants are assigned to each group

Which measure of proportion of variance tends to overestimate the size of an effect in a population? a. eta-squared b. omega-squared c. none of the above

a. eta-squared

A professor compared differences in class grades between students in their freshman, sophomore, junior and senior years of college. If different participants were in each group, the what type of statistical design is appropriate for this study? a. a two independent sample t-test b. a one-way between subjects ANOVA c. a two-way between subjects ANOVA d. both A and B

b. a one-way between subjects ANOVA

A researcher divides participants into groups that will engage in low, moderate, or intense levels of exercise. The total calories consumed by participants following the exercise are then recorded. What type of statistical design is appropriate for this study? a. a related samples t-test b. a two-independent sample t-test c. a one-way between-subject ANOVA d. both b and c

c. a one-way between-subject ANOVA

The source of variability associated with error variance in a one-way between subjects ANOVA is called: a. between-groups variability b. within-groups variability c. degrees of freedom d. both A and B

b. within-groups variability

A researcher matched 30 participants on intelligence (hence 15 pairs of participants), and then compared difference in emotional responsiveness to two experimental stimuli between each pair. For this test, what are the critical values, assuming a two-tailed test at a 0.05 level of significance? a. +- 2.042 b. +-2.045 c. +-2.131 d. +-2.145

d. +-2.145

T or F: The numerator of the test statistic for a one-way between subjects ANOVA is the mean variability associated with error.

False

T or F: The estimated standard error for difference scores is the denominator of the test statistic for a related samples t-test.

True

What are the degrees of freedom for the related samples t-test? a) (nD - 1) b) (n - 1) (n - 1) c) (n - 1) + (n - 1) d) (n - 1) - (n - 1)

a) (nD - 1)

It is most appropriate to report effect size with a significant result. Why is it generally inappropriate to report effect size with insignificant results? a) Because insignificant results will always have an effect size equal to 0. b) Because insignificant results indicate that an effect size is also insignificant. c) Because it makes little sense to report the size of an effect that you just concluded doesn't exist. d) Because the probability of the size of an effect varies depending on the significance of the result.

a) Because insignificant results will always have an effect size equal to 0. (not?)

All other things being equal, increasing the sample size will ________ the value of the test statistic for a related samples t-test. a. increase b. decrease c. have no effect on

a. increase

In a sample of 12 participants, a researcher estimates 80% CI for a sample with a mean of M=22.3 and an estimated standard error (Sm) of 4.7. What is the confidence interval at this level of confidence? a. 80% CI 12.1-32.5 b. 80% CI 17.6-27.0 c. 80% CI 15.9-28.7 d. There is not enough information to answer

c. 80% CI 15.9-28.7

One difference between a repeated measures design and a matched samples design in that: a. only one design is a type of related sample design b. only one design increases the power to observe an effect c. only one design involves observing the same participants in each group d. only one design eliminates between-persons variability

c. only one design involves observing the same participants in each group

How does the test statistic differ for a t-test using the repeated measures versus the matched samples design? a. using the matched samples design, we analyze raw scores, whereas using the repeated measures, we analyze difference scores before computing the test statistic for the related samples t-test b. using the repeated measures design, we analyze raw scores, whereas using the matched samples design, we analyze difference scores before computing the test statistic for the related samples t-test c. using the repeated measures design, we treat each pair of scores as related; we do not treat each pair of scores as related using the matched samples design. d. the test statistic for the repeated measures and the matched samples designs do not differ; the test statistic is computed the same.

d. the test statistic for the repeated measures and the matched samples designs do not differ; the test statistic is computed the same.

True or False: A one-way between-subjects ANOVA is conducted to test for mean differences between the levels of two or more factors.

false

True or False: A two-independent sample t-test is used when the same participants are observed in each of two groups.

false

True or False: When the difference between two groups is compared, the pooled standard deviation is used as an estimate for the population standard deviation in the effect size formula for estimated Cohen's d.

true

Without changing the value of error variance, the ____________ the between-groups variability, the more likely we are to reject the null hypothesis. a. larger b. smaller

a. larger

A type of related samples design in which participants are observed more than once is called a: a. repeated measures design b. matched pairs design c. matched samples design d. both B and C

a. repeated measures design

The source of variability associated with error variance in the one-way between-subjects ANOVA is called: a. between-groups variability b. within-groups variability c. degrees of freedom d. both A and B

b. within-groups variability

Following a significant one-way between subjects ANOVA in which k>2, what is the next appropriate step? a. summarize the data; no further tests are required b. interpret the data; no further tests are required c. conduct post hoc tests d. both A and B

c. conduct post hoc tests

Following a significant one-way between-subjects ANOVA in which k>2, what is the next appropriate step? a. summarize the data; no further tests are required b. interpret the data; no further tests are required c. conduct post hoc tests d. both A and B

c. conduct post hoc tests

All other things being equal, reducing the level of significance from 0.05 to 0.01 will ____________ the value of the test statistic for a related samples t-test. a. increase b. decrease c. have no effect on

c. have no effect on

One difference between a repeated measures design and a matched samples design is that: a. only one design is a type of related sample design b. only one design increases the power to observe an effect c. only one design involves observing the same participants in each group d. only one design eliminates between-persons variability

c. only one design involves observing the same participants in each group

Which of the following best describes the goal of estimation? a. to determine the extent to which a result is significant b. to estimate the significance of a result c. to narrow in on the true population mean by defining limits within which it is likely to be contained d. both A and B

c. to narrow in on the true population mean by defining limits within which it is likely to be contained

Which of the following is an assumption for computing any type of independent sample t-test? a) Data in the population being sampled are normally distributed. b) Data were obtained from a sample that was selected using a random sampling procedure. c) The probabilities of each measured outcome in a study are independent. d) all of the above

d) all of the above

Within group variance reflects: a. total variance in the experiment b. error variance only c. error variance plus treatment d. treatment variance only e. total variance plus treatment variance

b. error variance only

A researcher finds that the mean difference in productivity between employees working the morning shift (n = 16) and the night shift (n = 10) is 5.0 units, and the estimated standard error for the difference is 2.7 units. If the alternative hypothesis states that there is a difference in productivity, then is this result significant at a .05 level of significance? a) Yes, this result is significant. b) No, this result is not significant. c) There is not enough information to answer this question.

b) No, this result is not significant.

To compute a related samples t-test, a researcher has to know many values. Which of the following is NOT a value that the researcher must know to compute this test? a) the estimated standard error for difference scores b) the population variance of difference scores c) the sample size or number of pairs of scores d) the sample variance of difference scores

b) the population variance of difference scores

Which type of error is used to compute the confidence interval for one independent sample selected from a population with an unknown variance? a. standard error b. estimated standard error c. estimated standard error for the difference d. estimated standard error for the difference scores

b. estimated standard error

A researcher measures deviant behavior in a sample of 12 children from abusive homes (sample A). Another researcher measures the same behavior in a sample of 18 children from abusive homes (sample B). Which sample is associated with larger degrees of freedom? a. sample A b. sample B c. each sample has the same degrees of freedom d. there is not enough information to answer this question

b. sample B

To compute a related samples t-test, a researcher has to know many values. Which of the following is NOT a value that a researcher must know to compute this test? a. the estimated standard of error for difference scores b. the population variance of difference scores c. the same size or number of pairs of scores d. the sample variance of difference scores

b. the population variance of difference scores

A researcher conducts a study in which different participants are independently observed within groups, and the same participants are observed between groups. If there are only two groups, then what type of t-test is appropriate for this study? a. one-independent sample t-test b. two-independent sample t-test c. related samples t-test d. there is not enough information to answer this question

c. related samples t-test

A researcher sampled 25 participants and measured their alcohol consumption (in ounces) in both a home and a bar setting. If the mean difference in satisfaction ratings for this sample was 11.4+/-2.5 (Md+/-SD), then what is the decision at 0.05 level of significance? a. alcohol consumption significantly differed, t(23)=4.56 b. alcohol consumption significantly differed, t(24)=4.56 c. alcohol consumption significantly differed, t(23)=22.80 d. alcohol consumption significantly differed, t(24)=22.80

b. alcohol consumption significantly differed, t(24)=4.56

A researcher conducts a study and concludes that a new behavioral health treatment program significantly reduces one's risk for disease compared with risk levels in the general population (d = -0.64). Interpret the size of this effect. a) 64% of the variability in risk level can be accounted for by the new treatment. b) 64% of the new treatment can be accounted for by the risk levels. c) Risk levels in the population shifted 0.64 standard deviations below the mean. d) Risk levels in the population shifted 0.64 standard deviations above the mean.

c) Risk levels in the population shifted 0.64 standard deviations below the mean.

A researcher compares differences in positivity between participants in a low-, middle-, or upper-middle-class family. If she observes 15 participants in each group, then what are the degrees of freedom for the one-way between-subjects ANOVA? a. (2, 12) b. (3, 43) c. (2, 42) d. (3, 12)

c. (2, 42)

A professor teaches a certain section of material using a lot of examples with sports and cars to illustrate. He is concerned this may have biased his instruction to favor male students. To test this, he measures exam grades from this section of material among women (n=10) and men (n=10). The mean score in the male group was 84+/-4.0 (M+/-SD); in the female group, it was 78+/-8.0 (M+/-SD) points. If the null hypothesis is that there is no difference in exam scores, then test the null hypothesis at 0.05 level of significance. a. exam scores were significantly higher in male group, t(18)=2.83, p<0.05 b. exam scores were the same between groups, t(18)=2.12, p>0.05 c. exam scores were significantly higher in the male group, t(18)=2.12, p<0.05 d. exam scores were the same between groups, t(18)=1.00, p>0.05

c. exam scores were significantly higher in the male group, t(18)=2.12, p<0.05

A researcher placed male rodents in the presence and absence of a conspecific male. Cortisol (a stress hormone) levels were compared at both times. What type of t-test is most appropriate for this study? a. one-independent sample t-test b. two-independent sample t-test c. related samples t-test d. there is not enough information to answer this question

c. related samples t-test

T or F: A two-independent sample t-test is computed when mean differences are compared between two or more groups sampled from a population with an unknown variance.

False

True or False: The degree of freedom for a one-way between-subjects ANOVA is the sample size minus one.

false