Question 1

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):

Accepted Answer

A) 12 
B) 26 
C) 33 
D) 196

Question 2

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

Accepted Answer

The answer of When carrying out a t test for...

Question 3

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

Accepted Answer

The answer of When carrying out a t test for...

Question 4

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

Accepted Answer

A) it has slightly less scores at the extremes 
B) it has slightly more scores at the extremes 
C) it has an extra hump (i.e., bimodal) 
D) it does not differ

Question 5

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

Accepted Answer

A) look on a special table to find the estimated variance 
B) proceed normally, but interpret the results with caution 
C) divide the sum of squared deviations by N-1 instead of N 
D) multiply the sample's variance by the degrees of freedom

Question 6

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?

Accepted Answer

A) The hypothesis testing probably used one-tailed tests. 
B) The various scales all probably had just about the same population variances. 
C) The t scores are all larger than the raw change scores. 
D) The hypothesis testing probably used a t test for dependent means.

Question 7

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

Accepted Answer

A) it is based on using absolute deviations 
B) it is based on using squared deviations 
C) it tends to be slightly too large 
D) it tends to be slightly too small

Question 8

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 _________.

Accepted Answer

The answer of To find the score at which the...

Question 9

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.)

Accepted Answer

A) -2.62, 0, +2.62 
B) +2.262 
C) -2.262, 0 
D) -2.262, +2.262

Question 10

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?

Accepted Answer

A) 20/10 = 2.0 
B) 20/9 = 2.2 
C) 400/10 = 40.0 
D) 400/9 = 44.4

Question 11

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?

Accepted Answer

A) 5)2/-1.833 = -2.84 
B) 2/5.2 =. 38 
C) 5)2/2 = 2.60 
D)   /5.2 = .77

Question 12

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

Accepted Answer

The answer of When figuring the variance of the distribution...

Question 13

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

Accepted Answer

A) The population variance is known. 
B) The population mean is greater than the sample mean. 
C) The population follows a normal distribution. 
D) The sample follows a normal distribution.

Question 14

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?

Accepted Answer

A) 19 
B) 24 
C) 55 
D) nearly 1

Question 15

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

Accepted Answer

The answer of One can figure an unbiased estimate of...

Question 16

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

Accepted Answer

A) degrees of freedom 
B) number of scores minus 1 
C) number of scores multiplied by the standard deviation 
D) both A and B

Question 17

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:

Accepted Answer

A) the mean variance 
B) variance of the dependent means 
C) difference scores 
D) independent t scores

Question 18

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

Accepted Answer

A) True 
 B)False

Question 19

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

Accepted Answer

The answer of When you measure the same people before...

Question 20

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.

Accepted Answer

The answer of A consumer researcher was asked to test...

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) :