PSYC 3505 Behavioral Statistics

If a repeated-measures study shows a statistically significant difference between two treatments with α = 0.01, what can the researcher conclude about measures of effect size?

A statistically significant effect does not necessarily indicate that the effect size will be large

Which of the following statements about the comparison between effect size and power is correct?

As effect size increases, power also increases.

In general, if the variance of the difference scores increases, what will happen to the value of the t statistic?

It will decrease in magnitude (move toward 0 at the center of the distribution)

If two samples are selected from the same population, under which circumstances will the two samples have exactly the same t statistic?

The samples are the same size, have the same mean, and have the same variance

For the independent-measures t statistic, what is the effect of increasing the sample variances?

a decrease in the likelihood of rejecting H0 and a decrease in measures of effect size

A researcher plans to conduct a research study comparing two treatment conditions with a total of 20 participants. Which of the following designs would produce 20 scores in each treatment?

a repeated-measures design

A researcher is using a repeated-measures study to evaluate the difference between two treatments. If the difference between the treatments is consistent from one participant to another, then the data should produce ______.

a small variance for the difference scores and a small estimated standard error

For the independent-measures t statistic, what is the effect of increasing the difference between sample means?

an increase in the likelihood of rejecting H0 and an increase in measures of effect size

A researcher selects a sample from a population with µ = 30 and uses the sample to evaluate the effect of a treatment. After treatment, the sample has a mean of M = 32 and a variance of s 2 = 6. If Cohen's d is used to measure the size of the treatment effect, which of the following would have no effect on the value of Cohen's d?

an increased sample size

In a repeated-measures experiment, each individual participates in one treatment condition and then moves on to a second treatment condition. One major concern in this type of research study is that participation in the first treatment may influence an individual's score in the second treatment. What is this problem called?

an order effect

Which of the following is true regarding assumptions underlying the independent-measures t formula for hypothesis testing?

as the discrepancy in sample sizes increases, the assumption that the two populations from which the samples are selected must have equal variances becomes more important

Which of the following research situations would be most likely to use an independent-measures design?

compare the mathematics skills for 9th grade boys relative to 9th grade girls

An independent-measures research study uses a total of 40 participants to compare two treatment conditions. What is the df value for the t statistic computed for the corresponding hypothesis test?

df = 38

A repeated-measures research study and a separate independent-measures research study both produced a t statistic with df = 10. How many individuals participated in each research study?

n = 11 for a repeated-measures research study and n = 12 for an independent-measures research study

A researcher reports an independent-measures t statistic with df = 16. How many participants were in the entire study?

n = 18

A researcher reports t(22) = 5.30, p < 0.01, two tails for an independent-measures experiment. How many individuals participated in the entire experiment?

n = 24

A repeated-measures research design tends to have which of the following drawbacks?

the possibility for extraneous variables that occur over the passage of time to influence results

Larry wants to do everything possible to be in a position to detect that a treatment he has designed is effective given that it is actually effective. Which of the following should he do?

use an alpha (α) of 0.05 instead of 0.01

For which of the following situations would a repeated-measures research design be appropriate?

comparing pain tolerance with and without acupuncture needles

What statement below is consistent with making a Type II error?

concluding that a treatment has no effect when it really does

Under which circumstance can a very small treatment effect still be statistically significant?

if the sample size (n) is very large

If a hypothesis test is found to have power = 0.80, which is the probability that the test will result in a Type II error?

p = 0.20

A researcher obtains t(20) = +2.00 and MD = 9 for a repeated-measures study. If the researcher measures effect size using the percentage of variance accounted for, what value will be obtained for r 2?

r2 = 0.17

Assuming all other factors are held constant, if the df value for a two-tailed t test with α = 0.05 were increased from df = 6 to df = 20, what would happen to the critical values for t?

The critical values would move closer to t = 0

The null hypothesis for a repeated-measures test states which of the following?

The entire population will have a mean difference of µD = 0

A researcher completes a hypothesis test using a = .05. Based on the evidence from the sample, the researcher decides to reject the null hypothesis. Which statement below is true?

The researcher might have made a Type I error, but the probability is less than 5%

Which of the following is not an underlying assumption of hypothesis testing in the context of a research study?

The sample size must be greater than n = 30

Which of the following statements is not consistent with the assumptions necessary when computing a repeated-measures t statistic?

The scores between each treatment must be independent

A hypothesis test involves a comparison of which two elements?

research results from a sample and a hypothesis about a population

If the null hypothesis is true, which value is expected on average for the repeated-measures t statistic?

t = 0

Which of the following is not needed to compute a t statistic?

the value of the population variance or standard deviation

For which of the following situations would a repeated-measures design have the maximum advantage over an independent-measures design?

when very few subjects are available and individual differences are large

What is assumed by the homogeneity of variance assumption?

whether two populations have equal variances

An instructor is interested in whether frequent feedback in their course to a small sample of students influences student performance. The instructor knows that final class scores are normally distributed with µ = 85 and σ = 6. Which is the alternative hypothesis for this research study?

µ frequent feedback ≠ 85

A researcher is interested in whether a new teaching method influences the public speaking skills of students in an introductory to communications class. The researcher knows that public speaking skills in the class are normally distributed with µ = 10 and σ = 2. Which is the null hypothesis for this research study?

µ teaching method = 10

Which of the following is the correct null hypothesis for an independent-measures t test?

µ1 - µ2 = 0