Exam 9: Testing Means: Two- Independent-Sample T Test With Confidence Intervals

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 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?

A t test is associated with n - 1 degrees of freedom.

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.

The ________ is an inferential statistic used to determine the number of standard deviations in a t distribution that a sample mean deviates from the mean value or mean difference stated in the null hypothesis.

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

Computing a one-sample t test is appropriate when

The estimated standard error in the t statistic uses the ________ to estimate the ________ when the population variance is unknown.

A researcher measures mean health scores of children at a local school and compares these scores to the mean health score known in the general population.Assuming that the population variance is unknown,what type of t test is appropriate for this study?

A researcher reports that the mean difference in the body weight of rats following a pharmacological versus control treatment is 14 grams,with a pooled sample variance equal to 256.What is the effect size for this test using estimated Cohen's d?

When scores are measured in a single group,the sample standard deviation is used as an estimate of the population standard deviation in the effect size formula for estimated Cohen's d.

A one-sample t test will be undefined (denominator = 0)when the same score is recorded for all participants in a study.

A researcher conducts a study and concludes that a new behavioral health treatment program significantly reduces one's risk for disease compared with risk levels in the general population (d = -0.64).Interpret the size of this effect.

State the critical value(s)for a t test using a two-tailed test at a .05 level of significance: t(20).

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.

A local elementary school determined that the average number of volunteers for their "Step into Spring" annual fundraiser has been 14 persons on average (per event).After taking additional measures to recruit volunteers this year,they got 28 people to volunteer.Test whether these additional measures increased the number of volunteers at a .05 level of significance.

A researcher reports that stress levels among nurses are higher compared to stress levels in the general population,t(20)= 2.086,p = .05 (d = .12).Was this a one-tailed or a two-tailed test?

A researcher reports that the mean difference between two groups is 20.12 and the estimated standard error for the difference is 2.83.Hence,the conclusion must be to reject the null hypothesis for a two-tailed test at a .05 level of significance.

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