Chapter 10
What is the correct formula for Cohen's d for a paired-samples t test?
(M - μ)/s
Twenty-four students were assessed on a mindfulness measure both before and after completing a semester-long meditative yoga class. The critical t values for a two-tailed paired-samples test based on their data, with a p level of 0.05, are:
-2.069 and 2.069.
The critical cutoffs for a two-tailed, paired-samples t test with N = 9, at a p level of 0.01, are:
-3.356 and 3.356.
A researcher reports a paired-samples t test as: t(14) = 2.23, p < 0.05, d = 0.79. The value of the effect size measure here is:
0.79.
Psychology students took longer to complete a quiz when music was playing in the background than when there was no background noise: t(19) = -4.01, p < 0.05. What is the sample size in this study?
20
What is the paired-samples t statistic when using Mdifference = 9.0, s = 7.8, N = 17?
4.76
A researcher believes that a new training program will increase test scores. Previous research shows that test scores increase 8 points between the first and second administration of the test being used. This researcher believes his training program will cause a significant increase, beyond the expected 8 points. If a paired-samples t test is used by this researcher, what value would he expect to be at the center of the comparison distribution, a distribution of mean differences?
8
Credit card debt for 10 people was compared before a major economic crash (perhaps one like that of 2008) and then after economic recovery, let's say five years later. Which of the following is an appropriate null hypothesis for this research?
Credit card debt before the economic crash will be approximately the same as that after the economic recovery.
A paired-samples t test results in the following statistic: t(4) = 2.71. Using this test result, what decision should be made about a two-tailed hypothesis test at p = 0.05?
Fail to reject the null hypothesis because the test statistic does not exceed the critical cutoff.
A sports psychologist is interested in whether athletes tend to train harder after a win or a loss. To study this, she simulates winning and losing situations in her laboratory. She exposes 28 athletes to each situation and assesses the intensity of their training routine after each experience. How might she control the confounding variable of order effects in this within-groups design?
She could expose half of the athletes to the winning situation first and the other half to the losing situation first.
paired-samples t test
The paired-samples t test is used to compare two means for a within-groups design, a situation in which every participant is in both samples; also called a dependent-samples t test.
After performing a paired-samples t test as part of a hypothesis test, it is recommended by the APA that researchers also consider:
calculating a confidence interval and a measure of effect size.
For the paired-samples t test, the comparison distribution:
contains means of difference scores
A paired-samples t test is also known as a:
dependent-samples t test.
A group of students in a research class develop an educational video about academic integrity. They are interested in whether their video can increase students' knowledge about the topic. They recruit 42 students, assess their knowledge about academic integrity, show the video, and then reassess knowledge with the same questionnaire used earlier. According to the phenomenon of order effects, performance on the test of knowledge may be:
higher on its second administration simply because it has been seen once before.
counterbalancing
minimizes order effects by varying the order of presentation of different levels of the independent variable from one participant to the next.
A group of rats ran faster after receiving a steroid drug supplement than they did earlier without any drug supplement. What type of statistical test should be reported with these results?
paired-samples t test
In which statistical test does one calculate a difference score for each individual, take the mean of the difference scores, and perform a test on them to compare two sample means?
paired-samples t test
order effects
refer to how a participant's behavior changes when the dependent variable is presented for a second time, sometimes called practice effects.
A researcher calculates a confidence interval for a paired-samples t test. That interval is centered around -8.32, which is the:
sample mean difference.
The major difference between the paired-samples t test and the single-samples t test is that in the paired-samples t test:
we must create difference scores for every individual.
Doctors used a t test to compare cancer patients' recovery rates during time spent in the hospitals versus time spent in their own home to decide the best place for patients to be during recovery. Their study measured all patients' white blood cell counts while they were in the hospital and then again while all patients were at home. What type of design is this?
within-groups
