MSA622 EXAM 2 (CH 10) STUDY GUIDE

Participants in a study for a new medicine reported significantly less pain 30 min after taking the pill than before taking the pill, t(9) = 3.804, p < .05 (w2 = 0.56). In this related-samples t test, how many participants were observed? (Ch 10)

10

What is Estimated Standard Error for Difference Scores (SMD)? (Ch 10)

An estimate of the standard deviation of a sampling distribution of mean difference scores. It is an estimate of the standard error or standard distance that the mean difference scores deviate from the mean difference score stated in the null hypothesis

Distinguish between the repeated-measures design and the matched pairs design Ch 10)

Each participant is observed at least 2 times in the repeated-measure

What value is placed in the denominator of the test statistic for the realated-samples t test. (Ch 10)

Estimated standard error for difference scores

What are the assumptions for a related-samples t test? (Ch 10)

Normally and independence within groups

A researcher records the amount of computer use (in hrs/day) in a sample of students and then match the students based on their amount of computer use. Is this an example of matching though experimental manipulation or matching through natural occurrence ?(Ch 10)

Matching through experimental manipulation

Name 2 types of repeated-measures designs (Ch 10)

Pre-post design and with-in subjects design

What is Within-Subjects Design?

A type of repeated-measures design in which researchers observe the same participants across many treatments but not necessarily before and after a treatment

How do related samples differ from independent samples? (Ch 10)

-In related samples participants are related because they are either observed more than once or matched on common traits. -In Independent samples participants are not related because diff participants are observed in each group.

What is an error? (CH 10)

Refers to any unexplained difference that cannot be attributed to, or caused by, having different treatments. The standard error of the mean is used to measure the error or unexplained differences in a statistical design

What is a dependent sample? (CH 10)

A group or sample in which the participants are related. They are matched, experimentally or naturally,

What is Repeated-Measures Design? (CH 10)

A research design in which the same participants are observed in each group or treatment. Two types of repeated-measures designs are the pre-post design and the within-subjects design

What is Pre-Post Design? (Ch 10)

A type of repeated-measures design in which researchers measure a dependent variable for participants before (pre) and after (post) a treatment

What is Related-Samples t Test? (CH 10)

An inferential statistic used to test hypotheses concerning two related samples selected from populations in which the variance in one or both populations is unknown

What is a Related-Samples t Test? (CH 10)

An inferential statistic used to test hypotheses concerning two related samples selected from populations in which the variance in one or both populations is unknown

To compute the related-samples t test, we assume independence within groups and between groups, T/F? (Ch 10)

False

The degrees of freedom for the related-samples t test are the total number of participants minus one and not the total number of pairs minus one? (Ch 10)

False,

What is a Related Sample?

-A group or sample in which the participants are related. -observed in more than one group (a repeated-measures design), -or they are matched, experimentally or naturally, based on common characteristics or traits -(a matched-pairs design); also called a dependent sample

An example of matching by natural occurrence would be if we matched participants based on their gender (male, female). T/F? (Ch 10)

True

The repeated-measures design is associated with greater power to detect an effect compared with the independent-samples design? (Ch 10)

True

The test statistic for the related-samples t test is not equivalent to the test statistic for the two-independent-sample t test, T/F? (CH 1i0)

True

What is the value for the degrees of freedom for each example(Ch10) a. A study comparing 10 matched pairs of scores b. A study involving 18 participants observed 2 times

a. N-1 = 9 so 10-1 = 9 therefore df = 9 b. N-1 = 17 so 18-1 = 17 and 3, therefore df = 17, 3

The related samples design decreases ________ thereby increasing ________, compared to the two-independent-samples design? (Ch 10)

standard error, power

Why do we find the difference between pairs of scores (compute difference scores) before computing the test statistic for a related-samples t-test? (Ch 10)

Computing difference scores eliminates the between-persons error, thereby increasing the power of the test

All other things being equal, as the sample size decreases, what happens to the critical value for a related-samples t test? (or for any t test for that matter) (Ch 10)

The critical value increases

A professor computes the mean difference in aggressive responses from participants before and after watching a video showing violence as 9.0 ± 14.5 (MD ± SD), and this difference is significant. What is the effect size for this result using estimated Cohen's d? (Ch 10)

d= 0.62 (medium effect)

What is the denominator of the test statistic for a related-samples t test? (Ch 10)

The estimated error for difference scores

What is related sample? (CH 10)

A group or sample in which the participants are related. Participants can be related in one of two ways: They are observed in more than one group (a repeated-measures design), or they are matched, experimentally or naturally, based on common characteristics or traits (a matched-pairs design); also called a dependent sample

What is Matched-Pairs Design? (CH 10)

A research design in which pairs of participants are selected and then matched, either experimentally or naturally, based on common characteristics or traits; also called a matched-samples design or a matched-subjects design, matched-sample design

What is a Difference Score? (CH 10)

A score or value obtained by subtracting one score from another

Early experiments in learning showed that rats learned a maze quickly when rewarded. A researcher records the time taken for rats to learn a route in the presence and absence of food. If the researcher tested the hypothesis that presence of food would produce faster learning, at a .05 level of significance (two-tailed test), then what is her decision if she computes t = 2.842 in a sample of eight rats? (Ch 10)

Reject the null hypothesis, there is evidence for faster learning.

What is the numerator of the test statistic for a related-samples t test? (Ch 10)

it is the mean difference observed minus the mean difference stated in the null hypothesis

A researcher surveys the studying habits of students in his class and then matches them based on this survey, so he could study the effectiveness of group work. What is this procedure is called? (Ch 10)

matching through experimental design

A type of related samples design in which researchers measure a dependent variable for participants before and after a treatment is called a what?

pre-post design

A researcher selects a sample of 36 children for a memory task. The researcher finds that children remembered more pictures than words, t = 3.243. Use eta-squared to compute the proportion of variance for this result? (Ch 10)

η2 = 0.23