Question 1

Which of the following are assumptions underlying the use of the t test for independent groups?

Accepted Answer

A)  the variance of each population is known 
B)  the sampling distribution of  must be normal 
C)  the samples are drawn from populations having equal variances 
D)  all of these 
E)  the sampling distribution of  must be normal and the samples are drawn from populations having equal variances

Question 2

Compare and contrast the independent groups design with the correlated groups design.

Accepted Answer

The answer of Compare and contrast the independent groups design...

Question 3

With the t test for correlated groups, the difference between the sample means always equals the mean of the difference scores.

Accepted Answer

A) True 
 B)False

Question 4

An automotive engineer wishes to determine the fuel efficiency of a test engine compared to the standard production model. The following data (miles/gallon) were obtained under standard conditions. Assume independence between scores in each group.

Accepted Answer

The answer of An automotive engineer wishes to determine the...

Question 5

Define t test for correlated groups.

Accepted Answer

The answer of Define t test for correlated groups....

Question 6

As an owner of a computer component factory you want to buy a new machine to make integrated circuits. You can buy one of two types of machines. You obviously want to buy the better machine (we'll assume they are comparable in price and reliability). You rent both machines for 8 days and make sample runs on both machines. The following data are the number of defective components per 1000 on each day.

Accepted Answer

The answer of As an owner of a computer component...

Question 7

The use of the t test for independent groups assumes _________.

Accepted Answer

A)   is normally distributed 
B)  s 12 = s 22 
C)   is normally distributed 
D)  all of these 
E)   is normally distributed and s 12 = s 22

Question 8

In a correlated t test, if the independent variable has no effect, the sample difference scores are a random sample from a population where the mean difference score ( µ D ) equals _________.

Accepted Answer

A)  0 
B)  1 
C)  N 
D)  cannot be determined

Question 9

The t test for independent groups assumes homogeneity of variance.

Accepted Answer

A) True 
 B)False

Question 10

For the independent groups design, increasing sample variance decreases power.

Accepted Answer

A) True 
 B)False

Question 11

Define confidence-interval approach.

Accepted Answer

The answer of Define confidence-interval approach....

Question 12

How does the variability of the sample data affect the power of the t test? Explain, using the appropriate equations.

Accepted Answer

The answer of How does the variability of the sample...

Question 13

A worker in a neighborhood clinic wishes to assess the impact of showing an educational film on patient compliance in taking an antihypertension medication. The diastolic blood pressure (BP) is used as the dependent variable. During the study the medication dosage was kept constant. Blood pressure was measured one week prior to the film, then the film was shown, and the blood pressure measured again 3 weeks later. The data are shown below:

Accepted Answer

The answer of A worker in a neighborhood clinic wishes...

Question 14

A major advantage to using a two condition experiment (e.g. control and experimental groups) is _________.

Accepted Answer

A)  the test has more power 
B)  the data are easier to analyze 
C)  the experiment does not need to know population parameters 
D)  none of these are correct

Question 15

Which of the following increase(s) the power of the t test?

Accepted Answer

A)  increasing N 
B)  increasing the sample variance(s) 
C)  increasing the effect of the independent variable 
D)  all of these 
E)  increasing N and increasing the effect of the independent variable

Question 16

When a result is statistically significant, that guarantees that the result is an important one.

Accepted Answer

A) True 
 B)False

Question 17

If r between the scores of both groups is high and negative then the t test for correlated samples is not a powerful statistical test.

Accepted Answer

A) True 
 B)False

Question 18

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.

Accepted Answer

The answer of A professor of women's studies is interested...

Question 19

A school psychologist is interested in determining if children with attention deficit disorder (ADD) learn better if English literature is read to them rather than having them read the material themselves. A random sample of 10 sixth graders with ADD is selected and divided into two groups of 5 each. One of the groups has a story read to them (Listening Group) and the other reads the story themselves (Reading Group). A quiz on the story is given after each group has finished reading or hearing the story. The following scores were obtained with 20 being a perfect score.  Assume there is a real effect. The size of the effect, using equals _________.

Accepted Answer

A)  1.72 
B)  0.58 
C)  0.32 
D)  1.65

Question 20

A physical therapist wants to know if football players (guards in this experiment) recover full strength following injuries. A group of injury free guards were given a strength test as were a group of guards who had finished a rehabilitation program following an injury. The groups were matched in height and weight. The following strength ratings were recorded.  What do you conclude using a = 0.01 2 tail ?

Accepted Answer

A)  reject H0 
B)  retain H0

Exam 14: Students T Test for Correlated and Independent Groups

Which of the following are assumptions underlying the use of the t test for independent groups?

Compare and contrast the independent groups design with the correlated groups design.

With the t test for correlated groups, the difference between the sample means always equals the mean of the difference scores.

An automotive engineer wishes to determine the fuel efficiency of a test engine compared to the standard production model. The following data (miles/gallon) were obtained under standard conditions. Assume independence between scores in each group.

Define t test for correlated groups.

The use of the t test for independent groups assumes _________.

In a correlated t test, if the independent variable has no effect, the sample difference scores are a random sample from a population where the mean difference score ( µ D ) equals _________.

The t test for independent groups assumes homogeneity of variance.

For the independent groups design, increasing sample variance decreases power.

Define confidence-interval approach.

How does the variability of the sample data affect the power of the t test? Explain, using the appropriate equations.

A major advantage to using a two condition experiment (e.g. control and experimental groups) is _________.

Which of the following increase(s) the power of the t test?

When a result is statistically significant, that guarantees that the result is an important one.

If r between the scores of both groups is high and negative then the t test for correlated samples is not a powerful statistical test.