Stats Chapter 10

calculating CI for paired samples t test

1) draw pic with sample mean difference in the middle 2) indicate bounds 3) add in critical value (df table) 4) convert t statistic to raw scores mLower = -t(Sm) +Mdiff mUpper = t(Sm) +Miff

the six steps of the paired-samples t test

1) identify pop, distribution 2) state null and research 3) determine s, Sm, Mdifference 4) determine critical values (df on table) 4) calculate t statistic 5) make a decision

Calculate a paired-samples t statistic using the following information: 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

A paired-samples t test results in the following statistic: t(4) = 2.71. Using this test result, make a decision 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.

power caluclations for paired samples t test

Mcrit = µH0 +z (Smdiff) ZH1 = Mcrit - µH1/Smdiff

What is the confidence interval for a paired-samples t test with a mean difference of 4.6, a standard error of 0.16, and 9 df?

[4.24, 4.96]

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.

paired sample t test

compare two means for a within group design, every participant is in both samples

For the paired-samples t test, the comparison distribution:

contains means of difference scores.

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.

order effects

how a participants behavior changes when the dependent variable is present for a second time, people get better the second time around, use random sampling

.25 for r^2

large

t statistic for paired samples t test

mdiff - 0 / Sm

effect size for paired samples t test

mdiff-0/s

.09 for r^2

medium

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

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.

.01 for r^2

small

r^2 = ...

t^2 observed/t^2ovserved + DF

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.