Exam 9: The T Test for Independent Means

In an experiment with 48 participants, you are most likely to get a significant result if you assign __________ participants to the experimental group and __________ participants to the control group.

When conducting a t test for independent means, once the variances are known for each of the distributions of means, the variances can be added together to give the:

Results of a t test for independent means may be reported in a table where each significant difference is shown by __________.

In a certain study, an experimental group contains 45 participants while the control group contains 35 participants. What is the harmonic mean in this study?

A researcher hypothesizes that people of personality type K score higher than people of personality type R on an intelligence test. The S_Difference turned out to be .9, while the mean score of type K people was 18.8 and the mean score for type R people was 21.3. What is the t score?

The hypothesized effect size for a study involving a t test for independent means is the difference between the hypothesized population means, divided by __________.

t tests for independent means are usually reported in research articles with the means of the two groups plus the __________ , __________ , and __________.

Does training in a memory program affect memory for spontaneously observed events? A researcher arranged to train four volunteers in a memory program and four other volunteers served as controls. A week later, as part of their psychology class, all eight volunteers watched a film showing a bank robbery. Afterward they were questioned about the events. The number of accurate responses for the participants who had taken the memory course were 20, 25, 24, and 23. The number of correct responses for the control-group participants were 14, 22, 18, and 17. Do these results support the contention that those trained in this particular memory program are more accurate at recall for spontaneously observed events? (Use the .05 significance level.) a. Use the five steps of hypothesis testing. b. Figure the effect size. c. Explain what you did to a person who is familiar with the t test for a single sample but is unfamiliar with the t test for independent means.

In a t test for independent means, the weighted average of the estimates of the population variance from two samples is known as the:

In a t test for independent means, the difference between the means of your two samples is divided by the standard deviation of the __________ to get the t score.

For the following question(s): A sociologist interested in cultural differences compared women of two ethnic groups on a Role Approval Index (high scores mean high degrees of approval of one's social role). The results were as follows: Ethnic Group A: N = 15 M = 55 S² = 6.5 Ethnic Group B: N = 23 M = 51 S² = 4.5 -What is the pooled estimate of the population variance?

In a t test for independent means, once you have the two estimates of the population variance, the next step is to combine these to form a(n)__________.

In a t test for independent means, an effect size of __________ is considered large. (Provide a value.)

If the populations are highly __________ in opposite directions, the standard t test for independent means should not be used.

When conducting a t test for independent means, a typical null hypothesis is that the mean of Population 1 equals the mean of __________.

For each of the following studies, say whether you would use a t test for a single sample, t test for dependent means, or a t test for independent means. (a)A psychology researcher randomly assigns a group of 50 high school students to receive a new assertiveness training program and 45 other high school students to receive the standard after-school program that focuses on social skills. She later measures how well each group performs on a measure of interpersonal assertiveness. (b)A psychologist measures 100 patients in terms of their anxiety levels before and after undergoing a newly developed treatment. (c)The coach of your college football team conducts an informal survey showing that members of the team study an average of 3.5 hours per day. The coach makes the claim that this is equivalent to the amount of time students at the college study in general. You feel that the coach is incorrect. You randomly select 50 students from the college and ask them how much they study each day. Your result is that these 50 students study an average of 5.2 hours per day. (d)A researcher tests the memory scores of each of a group of 15 students twice, once while in a very noisy room and once while in a quiet room. She then compares the scores. (e)A researcher measures the intelligence of college students (n = 25)who are first born in their families compared to those who were born last in their families (n = 40).

A study has 6 participants in the experimental group and 16 participants in the control group. What is the harmonic mean of these sample sizes?

For the following question(s): Suppose a researcher wants to study the effectiveness of a new reading program for students who have not acquired the necessary reading skills by the time they reach the eighth grade. A randomly selected group of 50 students from a local junior high with poor reading skills will undergo the new reading program. Another group of 50 randomly selected students with poor reading skills will undergo regular reading classes. A month later, the reading skills of all 100 students are assessed to determine whether the program was successful. -Which of the following is a population of interest in this study?

You conduct a t test for independent means and reject the null hypothesis. This means that:

Because Sample 1 is sometimes bigger (or smaller)than Sample 2, a(n)__________ is used to combine the two estimates of the population variance into an overall pooled estimate.