Exam 9: Testing Means: One-Sample and Two-Independent Sample T Tests

A professor compares final exam scores in his psychology class to final exam grades in another comparable professor's class.Assuming that the population variance of exam scores is unknown,what type of t test is appropriate for analyzing differences between these classes?

A researcher reports a significant effect with t(14)= 3.24.Compute eta-squared for this result.

A researcher reports the following result for a two-tailed test at a .05 level of significance,t(24)= 2.010,and correctly decides to reject the null hypothesis.

As the degrees of freedom for a t test increase,the critical values for that test also increase.

A researcher records differences in ratings of emotion among participants watching either a drama or a romance film.Assuming that the population variance is unknown,what type of t test is appropriate for this study?

A one-sample t test will be t = 0 when the standard error was equal to 0.

A professor teaches a certain section of material using a lot of examples with sports and cars to illustrate.He is concerned that 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 a .05 level of significance.

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 key difference between a t statistic and a z statistic is that the standard error is ________ to compute a t statistic.

State the critical value(s)for a t test using a .05 level of significance in the lower tail only: t(24).

A researcher computes a two-independent sample t test and finds that the result is undefined (the denominator is equal to 0).This happens when there is no difference between the two groups .

A researcher conducts a study measuring differences in brain activity among rats placed on either a continuous or intermittent reward schedule.Assuming that the population variance in unknown,what type of t test is appropriate for this study?

A researcher selects a sample of 16 women and asks them to rate how important a sense of humor is in someone they want a long-term relationship with.She records scores averaging 1.6±0.8 (M±SD)on a rating scale from -3 (not important at all)to +3 (very important).Assuming that an average score of 0 is the null hypothesis,test whether or not women find this trait important at a .05 level of significance.

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

You read about a study testing whether night shift workers sleep the recommended 8 hours per day.Assuming that the population variance of sleep (per day)is unknown,what type of t test is appropriate for this study?

Measures of proportion of variance are computed the same for all t tests.

A t distribution with infinite degrees of freedom is a z distribution.

A researcher conducts two t tests.Test 1 is a two-tailed test with a smaller sample size at a .05 level of significance.Test 2 is a two-tailed test with a larger sample size at a .05 level of significance.What do you know about the degrees of freedom for each test?

A researcher reports a significant mean difference in a given population.If she computes both eta-squared and omega-squared to measure the effect size,then which estimate will be the most conservative?

Which of the following is an assumption for the two-independent sample t test,but not the one-sample t test?