Exam 9: The T Test for Independent Means

Based on the following results, which would be the correct use of the formula t = (M1-M2)/S_Difference? Sample 1: Mean = 60; Variance of the distribution of means = 2. Sample 2: Mean = 50; Variance of the distribution of means = 7.

What is the research hypothesis in this example?

For a study using a t test for independent means, the approximate number of participants needed for 80% power for an estimated large effect size and using a two-tailed test is:

An assumption for a t test for independent means is that each of the population distributions follows a normal curve. (True or False)

Cohen's conventions for the t test for independent means are approximately __________ for a small effect size, __________ for a medium effect size, and __________ for a large effect size.

For a study using a t test for independent means, the approximate number of participants needed for 80% power for an estimated small effect size and using a one-tailed test is:

Consider a study in which the population variance estimate based on an experimental group of 10 participants is 70, and the population variance estimate based on a control group of 20 participants is 50. Compute the pooled estimate of population variance.

The comparison distribution for a t test for independent means is a:

Suppose you carry out a study using a t test for independent means. The number of participants in each group is 40 and you conduct a one-tailed test. What would be the approximate level of power if you anticipated a medium effect size? (Consult the power table 9-4.)

Which of the following is the MOST serious violation of an assumption for the t test for independent means?

Consider a study in which the population variance estimate based on a treatment group of 14 participants is 8, and the population variance estimate based on a control group of 17 individuals is 9. Compute the pooled estimate of population variance.

"t = (Sample M-Population M)/ SM" is used to conduct a(n)__________.

For a t test for independent means, in order to determine the cutoff sample score on the comparison distribution at which the null hypothesis should be rejected, one should consult the __________.

The __________ is a hypothesis-testing procedure in which there are two separate groups of people tested and the population variance is not known.

The distribution of differences between means is essentially the same concept as the distribution of difference scores. (True or False)

Degrees of freedom 1 + Degrees of freedom 2 = __________

A theater department enlists the help of a social science professor to design a study to see if being surrounded by highly attractive people affects the performance of young actors. Each of 30 student actors is provided a script and asked to enact a particular scene with a group of other performers, and his/her performance is rated by a panel of judges. This enacting of the scene, however, occurs under one of two conditions, to which the actors are randomly assigned: For 13 of the actors, all the other performers are dressed and made up to look very attractive; for the other 17 actors, all the same other performers are made to look very unattractive. The mean performance ratings for the actors with attractive co-performers was 4.3 (S = .86); with unattractive co-performers, the mean was 5.4 (S = 1.30). Do these results suggest that acting with attractive co-performers affects performance? (Use the .05 significance level.) a. Use the five steps of hypothesis testing. b. Figure the effect size. c. Explain your findings.

When conducting a t test for independent means, a typical research hypothesis might be:

To conduct a t test for independent means, ideally the populations should both be normally distributed and have the same __________.

Many computer programs provide two sets of results for the t test for independent means. The standard method assumes that the population variances are __________ ; an alternative procedure takes into account that the population variances may be __________.