Stats Chapter 10

What are the degrees of freedom for the related samples t test?

(nD-1)

For the related samples t test, assuming that all other values remain constant, then as samples size increases,

all of the above (the value of the test statistic increases; the power to detect an effect increases; the estimate for standard error decreases)

Compared to the two-independent sample t test, the related samples design decreases

standard error

A researcher records the level of attention among 18 students during an interactive and lecture portion of a single class. If she computes a related samples t test at a .05 level of significance (two-tailed test), then what is the critical value for this test?

±2.110

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?

the population variance of difference scores

To increase the value of estimated Cohen's d, a researcher increases the sample size. Will this change the value of d?

No; the sample size is not used to compute effect size.

The related samples design can ________.

be more practical

A professor computes the mean difference in exam scores before and after a lecture as 9.0±14.5 (MD±SD), and this difference was significant. What is the effect size for this result using estimated Cohen's d?

d = 0.62 (medium effect)

The test statistic for a related samples t test makes tests concerning a single sample of

difference scores

A professor compares scores on a competency exam among students at two times during a single semester. What type of t test is most appropriate for this study?

related samples t test

Which of the following is the denominator of the test statistic for the related samples t test?

estimated standard error for difference scores

When reporting data in a results section, it is ____ necessary to identify the type of t test computed.

not

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?

related samples t test

Each of the following is needed to compute the estimated Cohen's d, except

standard error

A researcher selected a sample of 24 participants and observed their behavior at two times. The result of a related samples t test at a .05 level of significance was t = 2.68. Which of the following correctly describes the result of this test?

A related samples t test is the correct tests for this study; the result of the test is significant

The denominator of the test statistic for a related samples t test

provides an estimate of the error associated with the difference scores

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?

related sample t test

A researcher records the strength of a conditioned response among 12 rats in the presence and absence of conditioned cues. If he computes a related samples t test at a .05 level of significance (two-tailed test), then what are the critical values for this test?

±2.201

Two researchers analyze the same data set. Researcher A uses a two-independent sample t test and decides to retain the null hypothesis. Researcher B uses a related samples t test and decides to reject the null hypothesis. Which of the following is a likely explanation for the disparity in the decisions made.

The related samples t test had greater power to detect the effect.

Using APA format, which value is typically given in parentheses when reporting the results for a t test?

degrees of freedom

Which of the following identifies a large effect size for a t test?

η2= .25

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)?

The critical value decreases

"Elementary school children spent significantly more time reading the presence of a teacher than when the teacher was absent, t(7) = 2.804, p < .05 (ω2 = 0.46)." In this related samples t test, how many participants were observed?

8

Which of the following is an advantage for selecting related samples compared to selecting independent samples in behavioral research?

All of the above (Selecting related samples can be more practical.; Selecting related samples minimizes standard error.; Selecting related samples increases power.)

Which of the following is an assumption for computing the related samples t test?

All of the above (The population being sampled from is normally distributed.; The population variance of difference scores is unknown.; Samples are related or matched between groups, but not within groups.)

How does the test statistic differ for a t test using the repeated measures versus the matched samples design?

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

All other things being equal, reducing the level of significance from .05 to .01 will ________ the value of the test statistic for a related samples t test.

have no effect on

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

matched samples design

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?

related samples t test

A type of related samples design in which participants are observed more than once is called a

repeated measures design

Each of the following is an estimate of error for a t test, except

standard error

All other things being equal, as the degrees of freedom increase, what happens to the critical value for a related samples t test (or for any t test, for that matter)?

the critical value decreases

A researcher selects a sample of 24 college students and has them rate their liking for two advertisements aimed at improving the image of the college. The researcher finds that liking ratings significantly differed, t = 2.900. Use omega-squared to compute the proportion of variance for this result.

ω2= 0.24

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?

Sample B

A researcher computes the mean difference in locomotion in a sample of 12 rats before and 30 minutes after an injection of amphetamine. Rats were placed in a box with infrared beams. The number of times rats crossed the beams was used as a measure of locomotion. The mean difference in locomotion was 6.2±8.4 (MD±SD), and this difference was significant. What is the effect size for this result using estimated Cohen's d?

d = 0.74 (medium effect)

Which type of error is used to compute the confidence interval for two related samples selected from at least one population with an unknown variance?

estimated standard error for the difference scores

A researcher compares the difference in the amount of texting by students in class during the first week and last week of classes. The type of design described here is called a

repeated measure design

A researcher matched 30 participants on intelligence (hence 15 pairs of participants), and then compared differences 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 .05 level of significance?

±2.145

A researcher selects a sample of 36 dog owners and measures their responsiveness to pictures depicting the humane and inhumane treatment of dogs. The researcher finds that responsiveness significantly differed, t = 3.243. Use eta-squared to compute the proportion of variance for this result.

η2= 0.23

All other things being equal, increasing the sample size will ________ the value of the test statistic for a related samples t test.

increase

Each of the following is an advantage for using the related samples design, except

it increases the variability measured in a study

A researcher conducts a study in which the same participants are observed across each level of the independent variable. If there are only two levels of the independent variable, then what type of t test is appropriate for this study?

related samples t test

The related samples design can ________ the power to detect an effect by making the standard error ________.

increase; smaller

Which of the following is a type of related samples design in which different participants are actually observed in each group, but treated statistically as if they are the same persons in each group.

matched samples design

One difference between a repeated measures design and a matched samples design is that

only one design involves observing the same participants in each group

A researcher records the time it takes (in seconds) for participants to respond (by pressing a key) to a familiar versus an unfamiliar word flashed onto a computer screen. In this study, the difference in response time for each participant is compared. The type of design described here is called a

repeated measures design

Which of the following is the numerator of the test statistic for the related samples t test?

the mean difference observed minus the mean difference stated in a null hypothesis