Exam 10: The t Test for Two Independent Samples

An independent-measures study has one sample with n = 6 and a second sample with n = 8 to compare two experimental treatments.What is the df value for the t statistic for this study?

An independent-measures study with n = 20 scores in each treatment will produce an independent-measures t statistic with df = 19.

A researcher reports an independent-measures t statistic with df = 30.If the two samples are the same size (n₁ = n₂),then how many individuals are in each sample?

Confidence intervals with the independent-measures t statistic are used to estimate how much difference there is between two population means.

If other factors are held constant,which of the following sets of data is most likely to satisfy the homogeneity of variance assumption?

If other factors are held constant,which of the following sets of data is most likely to produce a significant mean difference?

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

An independent-measures study produces sample means of M₁ = 20 and M₂ = 17,and a pooled variance of 9.For this study,what is the value of Cohen's d?

If other factors are held constant,which of the following sets of data would produce the largest value for an independent-measures t statistic?

Which of the following sets of data would produce the largest value for Cohen's d?

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

The estimated standard error for the independent-measures t statistic provides a measure of how much difference should exist,on average,between two sample means when the null hypothesis is true.

An educational psychologist studies the effect of frequent testing on retention of class material.In one section of an introductory course,students are given quizzes each week.A second section of the same course receives only two tests during the semester.At the end of the semester,both sections receive the same final exam,and the scores are summarized below: Frequent Quizzes Two Exams n=20 n=20 M=73 M=68 a.If the first sample variance is s² = 38 and the second sample has s² = 42, do the data indicate that testing frequency has a significant effect on performance? Use a two- tailed test at the .05 level of significance.(Note: because the two samples are the same size, the pooled variance is simply the average of the two sample variances.) b.If the first sample variance has s² = 84 and the second sample has s² = 96, do the data indicate that testing frequency has a significant effect? Again, use a two-tailed test with α = .05. c.Describe how the size of the variance affects the outcome of the hypothesis test.

If other factors are held constant,the larger the two sample sizes,the greater the likelihood that the independent-measures t test will find a significant difference.

The results from an independent-measures t hypothesis test are reported as "t(24)= 3.85, p < .01,two tailed." The research study for this test used a total of 25 subjects.

If other factors are held constant,the larger the difference between the two sample means,the greater the likelihood that the independent-measures t test will find a significant difference.

The data from an independent-measures research study produce a sample mean difference of 4 points and a pooled variance of 18.If there are n = 4 scores in each sample,what is the estimated standard error for the sample mean difference?

If one sample has n = 5 scores with SS = 40 and a second sample has n = 5 scores with SS = 20,then the pooled variance will be 60/10 = 6.

The results from an independent-measures t hypothesis test are reported as "t(14)= 2.10, p > .05,two tailed." For this test,the null hypothesis was rejected.

A major company would like to assess the impact of using a professional trainer to conduct a confidence-building workshop with its salespeople.A sample of 16 workers is obtained.Half (n = 8)attend the workshop and the other half (n = 8)serve as a control group.Two weeks later,each of the participants is given a questionnaire measuring the level of self-confidence.The data are as follows: Workshop M=17.5 M=22.7 SS=100 SS=124 Use the sample data to construct an 80% confidence interval for the mean difference in confidence between the control group and the workshop conditions.