Which test?
For which of the following situations would a repeated-measures research design be appropriate?
a. comparing mathematical skills for girls versus boys at age 10
b. comparing pain tolerance with and without acupuncture needles
c. comparing self-esteem for students who participate in school athletics versus those who do not
d. comparing verbal solving skills for science majors versus art majors at a college
b. Comparing pain tolerance with and without acupuncture needles
A researcher conducts a hypothesis test using a one-sample t test. A sample of n = 582 with a M = 34 and s2 = 36 is selected from an unknown population. What is the df value for the t statistic?
581
A repeated-measures research design tends to have which of the following drawbacks?
a. the possibility for extraneous variables that occur over the passage of time to influence results
b. the need for a larger sample size
c. less of an ability to control the extent to which individual differences among research participants influence results
d. the need to provide more evidence to support statistical significance than other research designs
a. the possibility for extraneous variables that occur over the passage of time to influence results
Mothers with young children often complain that they do not get enough sleep. Suppose that you obtained a measure of the typical amount of sleep of nine mothers of children under 1 year of age and found the average hours of sleep to be M=7.2.
The sample standard deviation is .5124. Test whether the mean amount of sleep for these mothers differ significantly from a hypothesized population mean of 7.7 hours sleep per night. Use a two-tailed α = .05.
Reject the Null. Mothers are getting significantly less sleep.
Which of the following research situations would be most likely to use a repeated-measures design?
a. examine the development of vocabulary as a group of children mature from age 2 to age 3
b. compare the mathematics skills for CSULB student to all college student in the country
c. compare the mathematics skills for 9th-grade A track students relative to 9th-grade B track students
d. compare the blood-pressure readings before medication and after medication for a group of patients with high blood pressure
a. examine the development of vocabulary as a group of children mature from age 2 to age 3
An independent-measures study comparing two treatment conditions produces a t statistic with df = 38. If the two samples are the same size, how many participants were in each of the samples?
20
If difference scores begin to pile up away from a sample mean difference score of MD = 0, which of the following statements is true?
a. The null hypothesis will likely fail to be rejected.
b. The null hypothesis will likely be rejected.
c. The sample size is large.
d. The critical region is small.
b. The null hypothesis will likely be rejected.
A researcher predicts that scores in treatment A will be higher than scores in treatment B. If the mean for the n = 10 participants in treatment A is 4 points higher than the mean for the n = 10 participants in treatment B and the data produce t = 1.985, which decision should be made? (Evaluate with alpha .05 and alpha .01)
Fail to reject H0 if a = 0.05 and if a = 0.01
A researcher investigated whether a specific type of training from a sports psychologist administered to college tennis players would lead to higher accuracy. The shot accuracy of 15 tennis players was recorded before and after receiving eight weeks of training from a sports psychologist (accuracy scores ranged from 0 to 100, with higher scores indicating greater accuracy). What kind of test and how many tails?
One-tailed, Repeated Measures t Test
A repeated-measures study using a sample of n = 40 participants would produce a t statistic with df = _____.
39
Conceptually, what does the null hypothesis of a one-tailed repeated-measures research study put forth if a treatment is expected to increase scores on a questionnaire, relative to pre-test scores on a questionnaire?
a. There is a decrease in scores after treatment.
b. There is an increase in scores after treatment.
c. There is no decrease in scores after treatment.
d. There is no increase in scores after treatment.
d. There is no increase in scores after treatment.
A researcher conducts a repeated-measures study to evaluate the efficacy of therapy in increasing positive coping skills. The researcher examines positive coping skills before and after therapy with a sample of n = 6 participants and obtains a sample mean difference of MD = 10 with an estimated standard error of sMD = 4.78. What is the correct decision for a one-tailed hypothesis test in which therapy is expected to increase positive coping skills? (Evaluate with alpha .05 and alpha .01)
Reject the null hypothesis with α = 0.05 but not with α = 0.01
1.Mothers with young children often complain that they do not get enough sleep. Suppose that you obtained a measure of the typical amount of sleep of nine mothers of children under 1 year of age and found the following durations (in hours): 6.4, 7.5, 6.9, 7.3, 7.6, 7.1, 6.5, 7.7, 7.8.
The sample standard deviation is .51235. Test whether the mean amount of sleep for these mothers differ significantly from a hypothesized population mean of 7.7 hours sleep per night.
What kind of test and how many tails?
A researcher uses a repeated-measures study to compare two treatment conditions with a set of 20 scores in each treatment. What is the value of df for the repeated-measures t statistic?
19
In general, what characteristics of difference scores are most likely to produce a statistically significant t statistic for a repeated-measures hypothesis test?
a. a large sample size and a large variance
b. a large sample size and a small variance
c. a small sample size and a large variance
d. a small sample size and a small variance
b. a large sample size and a small variance
A researcher conducts a repeated-measures study to evaluate the efficacy of therapy in decreasing maladaptive behavior. The researcher examines maladaptive behavior before and after therapy with a sample of n = 6 participants and obtains a sample mean difference of MD = 6 with an estimated standard error of sMD = 3.00. What is the correct decision for a one-tailed hypothesis test in which therapy is expected to reduce maladaptive behavior? (Evaluate with alpha .05 and alpha .01)
Fail to reject the null hypothesis with both α = 0.05 and α = 0.01
Motivational speakers want to be perceived as trustworthy. One hypothesis is that speakers who exhibit immediacy behaviors such as making eye contact, smiling, and leaning forward will be perceived as more trustworthy than those who do not engage in these behaviors. To test this hypothesis, a psychologist obtained data from 26 participants. For people in a non-immediacy group, the speaker did not engage in any immediacy behaviors. For the immediacy group, however, the speaker made eye contact, smiled and leaned forward while giving a speech. After the speech, participants rated the speaker on a scale of trustworthiness ranging from 1 (not at all trustworthy) to 9 (highly trustworthy). Both groups had the same amount of participants. What kind of test and how many tails?
One-tailed, Independent Samples t Test
A repeated-measures research study and a separate independent-measures research study both produced a t statistic with df = 10. How many individuals participated in each research study?
n = 11 for a repeated-measures research study and n = 12 for an independent-measures research study
Compared to an independent-measures design, a repeated-measures study is more likely to find a statistically significant effect because it reduces the contribution of variance due to _____.
a. time-related factors
b. order effects
c. the effect of the treatment
d. individual differences
d. individual differences
Motivational speakers want to be perceived as trustworthy. One hypothesis is that speakers who exhibit immediacy behaviors such as making eye contact, smiling and leaning forward might be perceived as more trustworthy than those who do not engage in these behaviors. To test this hypothesis, a psychologist obtained data from 17 participants. What decision would you make using a two-tailed test with an alpha of .01?
No Immediacy Group
n = 8 / M = 4.77
Immediacy Group
n = 9 / M = 6.84
t = -3.744
Reject the null. Immediacy behaviors help speakers appear significantly more trustworthy.