Please circle either A, B, C, or D. Choose the BEST answer.
- (1 Point) The null hypothesis is the hypothesis that states that…
A. there is no difference.
B. there is a difference.
C. there may be a difference.
D. None of the above. - (1 Point) When testing a null hypothesis, the level of significance is the probability that…
A. a true hypothesis is rejected.
B. a true hypothesis is not rejected.
C. a false hypothesis is rejected.
D. a false hypothesis is not rejected. - (1 Point) As the sample size increases, the difference between the normal distribution and the
corresponding t distribution…
A. increases.
B. remains the same.
C. decreases.
D. There is no comparison. - (1 Point) When the null hypothesis is rejected…
A. p < beta. B. p > alpha.
C. p > beta.
D. p < alpha.
2 - (1 Point) The use of hypothesis testing for the Independent t Test does not include…
A. a decision to use a one- or two-tailed test.
B. a sampling distribution of the statistic.
C. use of the population variances.
D. group differences due to sampling fluctuation. - (1 Point) With all other factors held constant, decreasing the alpha level from .05 to .01 will
cause the power of the test to…
A. decrease.
B. remain the same.
C. increase.
D. become unimportant. - (1 Point) When applied to the Independent t Test, p > .05 means that…
A. the population means are not significantly different.
B. the sample means are not significantly different.
C. there is statistical significance for a one-tailed test.
D. None of the above. - (1 Point) Which of the following studies would use dependent samples?
A. A two-year study comparing the number of cavities in children who receive fluoride
treatment to those in children who do not receive fluoride treatment.
B. A two-year study comparing the number of cavities in children in affluent homes versus
children in homes that are below the poverty line.
C. A two-year study comparing the number of cavities in 8- to 10-year-old children before
and after the application of fluoride.
D. None of the above.
True/False:
Please write either “T” for True or “F” for False. If False, indicate WHY it is false, and
correct the statement to make it True. - (.5 Points) In general, it is better to determine power as a study is being planned. This is called
post hoc power.
3 - (.5 Points) It is appropriate to use Welch’s t Test when the population variances are unequal
and the sample sizes are unequal. - (.5 Points) The degrees of freedom are calculated as n – 1 for both the Independent and
Dependent t Tests. - (.5 Points) The assumptions for the One Sample t Test include normality and homogeneity of
variances.
Short Answer: - (1 Point) Explain in two to three sentences what is meant by practical significance.
- (1 Point) There are five factors that determine power. Choose one and describe it in your own
words. Reinforce your description with formulas or graphics. Be as descriptive as possible.
4 - (1 Point) List the assumptions for an Independent t Test. Choose one and explain it in your
own words.
Computational (Round to TWO decimal places when necessary): - (2 Points) A therapist specializing in depression wants to determine if his clients are
improving this year compared to previous years. Since his practice began, his clients have had
an average score on a happiness measure of 80. The therapist randomly samples n = 16 clients
from the current year and finds that their mean happiness score is 86 (s = 8). State the null and
alternative hypotheses. Be sure to indicate if this is a one-tailed or two-tailed test. What is the cv?
Use α = .05. Calculate the t statistic. What is your decision (i.e., accept or reject the null)?
Describe the results in your own words.
5 - (4 Points) A researcher would like to examine the effect of hypnosis on cigarette smoking.
The researcher selects a sample of smokers (n = 4) for the study and records the number of
cigarettes smoked on the day prior to treatment. The participants are then hypnotized and given
the posthypnotic suggestion that each time they light a cigarette, they will experience a horrible
taste and feel nauseous. The data for all four participants are below. State the null and alternative
hypotheses. Be sure to indicate if this is a one-tailed or two-tailed test. What is the cv? Use α =
.05. Calculate the t statistic. The only value that is provided is sd = 4. What is your decision (i.e.,
accept or reject the null)? Describe the results in your own words. Calculate the 95% CI and
interpret it. Calculate the effect size and interpret it.
Before After D
1 19 12 7
2 35 36 -1
3 20 13 7
4 31 24 7
6 - (4 Points) A researcher is investigating if 14-year-old boys and girls differ in sociability on
average. She collects the following information below (i.e., scores on a sociability measure).
Assume that there are statistically equal variances. State the null and alternative hypotheses. Be
sure to indicate if this is a one-tailed or two-tailed test. What is the cv? Use α = .05. Calculate the
t statistic. What is your decision (i.e., accept or reject the null)? Describe the results in your own
words. Calculate the 95% CI and interpret it. Calculate the effect size and interpret it.
Boys Girls
n 62 62
80 83
s
2 15 20
7 - (2 Points) A public health nurse is comparing the effectiveness of two weight loss programs
to see if there is a difference in the average amount of weight loss reported by clients in either
program (i.e., Program A and Program B). The following data were collected from clients in
each program after six months of participation. The SPSS output has been provided to answer the
following questions. State the null and alternative hypotheses. Be sure to indicate if this is a
one-tailed or two-tailed test. What is the cv? Use α = .05. BE CAREFUL HERE! Assume that
the normality assumption is satisfied. Calculate the t statistic (i.e., it should be approximately the
same value as in the SPSS output). Make sure you use the correct formula (i.e., the “regular”
Independent t Test or Welch t Test). You will know which formula to use based on the
homogeneity of variances assumption. What is your decision (i.e., accept or reject the null)?
Describe the results in your own words. Calculate the 95% CI and interpret it. Calculate the
effect size and interpret it.
Program A Program B
25 15
21 17
18 12
20 11
22 19
30 14
18
16
10
9
13
8
Extra Credit: - (1 Point) I assert that the critical value of t, for a One sample t Test with a nondirectional
alternative hypothesis and using a particular α level, will increase as sample size increases. Am I
correct? Circle “YES” or “NO.” If NO, explain why not?
YES NO