Question 195 out of 5 pointsWhy is it necessary to use the pooled variance when conducting an independent-samples t test?Selected Answer:Independent-samples t test work with two samples and an estimate of spread based on two samples is likely to be more accurate than an estimate of spread based on a single sample.Answers:Independent-samples t test work with two samples and an estimate of spread based on two samples is likely to be more accurate than an estimate of spread based on a single sample.

It is necessary to estimate the standard deviation of the two samples in order to compare the two samples to one another.Estimating the spread of the sample using the pooled variance increases the generalizability of results.Using the pooled variance from the two samples helps the researcher to identify skewness.

Question 205 out of 5 pointsResearchers were interested in whether relaxation training decreases the number ofheadaches a person experiences. They randomly assigned 20 participants to a control group (no relaxation training) or a relaxation training group and noted the change in number of headaches each group reported from the week before training to the week after training. The independent variable in this study is:

Question 65 out of 5 pointsMehl (2007) published in the journal Science the results of an extensive study of 396men and women, comparing the number of words uttered per day by each sex. Is thepopulation likely to be normally distributed? Why or why not?

Question 70 out of 5 pointsTo calculate a confidence interval for an independent-samples t test, use the difference between the means for the samples and the _____.