Exam 8: Introduction to the T Test: Single Sample and Dependent Means

Approximately how many research participants would be required for 80% power for a study using the t test for dependent means (assume a one-tailed hypothesis with an expected medium effect size of .50):

When carrying out a t test for dependent means, an effect size of .2 is considered to be __________.

When carrying out a t test for dependent means, an effect size of __________ is considered to be medium.

In what important way does a t distribution differ from a normal curve?

When estimating the population's variance from the scores in a sample, you should:

For the following question(s): A research article included the following table: Mean Score on Four Questionnaire Scales Before and After the Experimental Manipulation Questionnaire Before After Change Dominance 18.42 16.31 -2.11 Independence 17.25 21.38 4.13** Conformity 18.97 17.20-1.77* Nurturance 16.11 13.89 -2.22* ______________________ *p < .05; **p < .01 -Which of the following is most likely to be true given the information on this table?

When estimating the variance of a population from the sample, you cannot use the sample's variance directly because:

To find the score at which the null hypothesis will be rejected, you look on a t table. But first, you need to know the significance level, degrees of freedom, and _________.

For the following question(s): A school counselor claims that he has developed a technique to reduce prestudying procrastination in students. He has students time their procrastination for a week and uses this as a pretest (before)indicator of procrastination. Students then attend a workshop in which they are instructed to do a specific warming-up exercise for studying by focusing on a pleasant activity. For the next week, students again time their procrastination. The counselor then uses the time from this week as the posttest (after)measure. -Presume the counselor wants to examine whether there is a change (either an increase or decrease)in procrastination after attending his workshop. If the counselor tests 10 students using the .05 level of significance, what cutoff t score(s)will he use? (You should be able to figure this out without a table.)

For the following question(s): A school counselor claims that he has developed a technique to reduce prestudying procrastination in students. He has students time their procrastination for a week and uses this as a pretest (before)indicator of procrastination. Students then attend a workshop in which they are instructed to do a specific warming-up exercise for studying by focusing on a pleasant activity. For the next week, students again time their procrastination. The counselor then uses the time from this week as the posttest (after)measure. -A researcher conducts a t test for dependent means with 10 participants. The estimated population variance of the change scores is 20. What is the variance of the distribution of the means of change scores?

For the following question(s): A researcher conducts a t test for dependent means in which it is predicted that there will be a decrease in unemployment from before to after a particular job-skills training program. The cutoff t needed is -1.833. The standard deviation of the distribution of means of change scores is 2.0 and the mean change score for the sample studied is an increase of 5.2. -What is the t score?

When figuring the variance of the distribution of means based on an estimated population variance, you divide the estimated population variance by __________.

Which of the following is an assumption for the t test for dependent means?

What is the approximate power for a study using the t test for dependent means with an expected small effect size (.20), two-tailed test, N = 40?

One can figure an unbiased estimate of the population variance by dividing the sum of squared deviation scores by __________.

The number of scores free to vary when estimating a population parameter is/are:

You do a t test for dependent means in exactly the same way as a t test for a single sample, except that you use something called:

Degrees' of freedom is calculated as the number of scores minus the mean. (True or False)

When you measure the same people before and after some social or psychological intervention, this specific kind of repeated-measures situation is called a __________.

A consumer researcher was asked to test a claim by a franchise swimming instruction program. Specifically, they claimed that they could teach the average 7-year-old to swim across an Olympic-size pool in less than 2 hours. The researcher arranged for eight randomly selected 7-year-old children to take instruction at this school and kept a careful record of how long it took each child. The times (in minutes)were 60, 120, 110, 80, 70, 90, 100, and 130. What should the researcher conclude? Carry out a t test for a single sample (120 minutes is the "known" population mean)using the .01 significance level. a. Use the five steps of hypothesis testing. b. Explain what you did to a person who is familiar with hypothesis testing with a known population variance and a single sample, including understanding decision errors, effect size and power but knows nothing about t tests of any kind. Be sure to explain how this problem differs from a problem with a known population variance and a single sample.