Chapter 9: Define a two-independent sample t-test

Chapter 9: Define a two-independent sample t-test

Chapter 9: Define a two-independent sample t-test

• What is a between subjects design?  How does this differ from within subjects?
• Define a two-independent sample t-test.
• What are the assumptions associated with a two-independent sample t-test?
• A researcher measures the time it takes 13 men and 15 women to complete multiple tasks in a study. She compares the mean difference between men and women using the two-independent-sample t test. What is the critical value for this test if she conducts a two-tailed test at a .05 level of significance?
• What is the denominator for computing an estimated Cohen’s d for a two-independent-sample t test?
• If the difference between two means is 4, then what will the estimated Cohen’s d value be with a pooled sample standard deviation of each of the following?

(a)   4 (b)   8 (c)   16 (d)   40

• How do you calculate the degrees of freedom for a 2-independent sample t-test?
• What is the pooled sample variance?  Pooled sample standard deviation?
• When an independent sample is selected, are the same or different participants observed in each group?
•  Name three measures used to estimate effect size for the two-independent-sample t test.
• What are the three steps to compute an estimation formula?
•   In the following studies, state whether you would use a one-sample t test or a two-independent-sample t test.

(a)    A study measuring differences in attitudes about morality among men and women (b)    A study testing whether night-shift workers sleep the recommended 8 hours per day (c)    An experiment measuring differences in brain activity among rats placed on either a continuous or an intermittent reward schedule.

• Will each of the following increase, decrease, or have no effect on the value of the test statistic for a two-independent-sample t test?

(a)    The total sample size is increased. (b)    The level of significance is reduced from .05 to .01. (c)    The pooled sample variance is doubled.

• When is the t-test for independent means appropriate to use?
• How should the t value be interpreted?  How do we know what it means?  For example, when t(28) = -0.16, p. n.s. – what does this mean?