Exam 14: Students T Test for Correlated and Independent Groups

If = 0, then H₀ must be true.

Which of the following is (are) major advantage(s) of a two condition experiment over a single sample design?

Using Cohen's criteria, the size of effect found in problem 59 is _________.

For both the t test for repeated measures and independent groups, df = n 1 + n 2 - 2.

In an independent groups experiment, if the independent variable has no effect, µ 1 ≠ µ 2 .

A professor of women's studies is interested in determining if stress affects the menstrual cycle. Ten women are randomly sampled for an experiment and randomly divided into two groups. One of the groups is subjected to high stress for two months while the other lives in a relatively stress-free environment. The professor measures the menstrual cycle (in days) of each woman during the second month. The following data are obtained. Assume you are evaluating H ₀ using the t test. Using a = .05 2 tail , t crit = _________.

A medical researcher wishes to evaluate the effectiveness of a drug in prolonging the life of a red cell in a culture medium. Seven cultures are treated with saline (an inactive control substance) and seven others are treated with the new drug. The following survival times in days were recorded:

If a violation of the homogeneity of variance assumption occurs, it is always necessary to abandon use of the t test for an independent groups design.

It is not necessary to measure the population parameters to apply the t test for either the independent or correlated groups designs.

What are the assumptions underlying the t test for independent groups.

The confidence interval approach for evaluating the effect of the independent variable does not allow evaluation of the size of real effect.

A correlated groups design is more sensitive than an independent groups design if _________.

Used in conjunction with the correlated groups t test, only measures the direction of the effect.

A health educator wants to evaluate the effect of a dental film on the frequency with which children brush their teeth. A random selection of 8 children are used for the experiment. First, a baseline of the number of times the children brush their teeth over a month's period is established. Next, the children are shown the dental film and again the number of teeth brushings are recorded for a month. The following data are recorded. Using a = 0.05 2 tail , what do you conclude?

A health educator wants to evaluate the effect of a dental film on the frequency with which children brush their teeth. A random selection of 8 children are used for the experiment. First, a baseline of the number of times the children brush their teeth over a month's period is established. Next, the children are shown the dental film and again the number of teeth brushings are recorded for a month. The following data are recorded. Assume you are evaluating H 0 with the t test. The df for determining t crit equal _________.

The t test for correlated groups is generally more powerful than the sign test.

Five students were tested before and after taking a class to improve their study habits. They were given articles to read which contained a known number of facts in each story. After the story each student listed as many facts as he/she could recall. The following data was recorded. Assume there is a real effect. using , the size of effect for the improvement, equals _________.

In the t test for independent groups, the unbiased estimate of the population variance 2 is _________.

The t test is _________ likely to result in a Type II error than the sign test for a repeated measures design.

The estimate of s 2 used in the t test for independent groups is an estimated based on the variances of both samples.