Deck 9: The T Test for Independent Groups Samples

Question 1

In the formula for an independent-groups t test, the denominator in the equation represents:

A) the standard error of the mean.
B) the estimated standard error of the mean.
C) the standard deviation.
D) the standard error of the difference between means.

Answer 1

the standard error of the difference between means.

Question 2

If an independent-groups t test is equal to zero, then:

A) the two sample means differ significantly.
B) the two sample means do not differ significantly.
C) there is something wrong with the calculation.
D) the two population means differ significantly.

Answer 2

the two sample means do not differ significantly.

Question 3

If the null hypothesis is true, then the t test should be close to:

A) 0.00.
B) $\pm$ 1.65.
C) $\pm$ 1.96.
D) $\pm$ 3.00.

Answer 3

0.00.

Question 4

If the null hypothesis is not supported, then the t test should be:

A) 0.00.
B) ±1.00.
C) greater than ±1.00.
D) a negative number.

Question 5

Imagine that you conducted an independent-groups t test with 15 subjects in each group. For a one-tailed test, the t_cv at $\alpha$ = .05 would be:

A) $\pm$ 1.701.
B) $\pm$ 2.074.
C) $\pm$ 1.711.
D) $\pm$ 2.064.

Question 6

Imagine that you conducted an independent-groups t test with 7 subjects in each group. For a two-tailed test, the t_cv at $\alpha$ = .05 would be:

A) $\pm$ 1.717.
B) $\pm$ 2.074.
C) $\pm$ 1.711.
D) $\pm$ 2.179.

Question 7

If a researcher reported for an independent-groups t test that t(12) = 3.66, p < .01, how many subjects were there in the study?

A) 12
B) 14
C) 13
D) 9

Question 8

If a researcher reported for an independent-groups t test that t(22) = 2.69, p < .01, how many subjects were there in the study?

A) 24
B) 20
C) 11
D) 21

Question 9

$\mu$

-The alternative hypothesis for a two-tailed independent-groups t test states that:

A) H₀: $\mu$ ₁ $\not=$$\mu$ ₂.
B) H₀: $\mu$ ₁ = $\mu$ ₂.
C) H_a: $\mu$ ₁ $\not=$$\mu$ ₂.
D) H_a: $\mu$ ₁ = $\mu$ ₂.

Question 10

The null hypothesis for a one-tailed independent-groups t test states that:

A) H₀: $\mu$ ₁ $\geq$ $\mu$ ₂, or H₀: $\mu$ ₁ $\leq$ $\mu$ ₂.
B) H₀: $\mu$ ₁ = $\mu$ ₂.
C) H_a: $\mu$ ₁ $\not =$$\mu$ ₂.
D) H_a: $\mu$ ₁ $\leq$ $\mu$ ₂.

Question 11

The alternative hypothesis for a one-tailed independent-groups t test states that:

A) H₀: $\mu$ ₁ $\not =$$\mu$ ₂.
B) H₀: $\mu$ ₁ < $\mu$ ₂.
C) H_a: $\mu$ ₁ $\not=$$\mu$ ₂.
D) H_a: $\mu$ ₁ > $\mu$ ₂, or H_a: $\mu$ ₁ < $\mu$ ₂.

Question 12

If an independent-groups t test has 10 subjects in each group, then the degrees of freedom are:

A) 9.
B) 10.
C) 20.
D) 18.

Question 13

If an independent-groups t test has 13 subjects in each group, then the degrees of freedom are:

A) 26.
B) 24.
C) 13.
D) 12.

Question 14

For an independent-groups t test, effect size can be measured using:

A) Cohen's d.
B) the standard error of the difference between means.
C) r².
D) either Cohen's d or r².

Question 15

Which of the following is an assumption of the t test for independent groups?

A) The data are interval or ratio.
B) The underlying distributions are bell-shaped.
C) The observations are independent.
D) All of the above are assumptions of the t test for independent groups.

Question 16

t(14) = 3.35, one-tailed. Based on these results, we _____.

A) reject H_o
B) fail to reject H_o
C) accept H_o
D) reject H_a

Question 17

t(20) = 1.99, two-tailed. Based on these results, we _____.

A) reject H_o
B) fail to reject H_o
C) accept H_a
D) fail to reject H_a

Question 18

According to some research, males have better spatial skills than do females; and according to other research, females have better reading skills than males. A student is interested in determining which gender performs better on a word-search puzzle (a puzzle in which words are hidden vertically, horizontally, and diagonally within an array of letters) since this type of puzzle involves both spatial and reading skills. A sample of males and females volunteers to participate. They are given 10 minutes to work on a 50-word puzzle. The number of words correctly recognized is recorded for each subject, and the resulting data are as follows:
Conduct the appropriate analysis of these data, and determine whether there are any significant differences.

Question 19

A college student is interested in whether there is a difference between male and female students in the amount of time spent working out each week. The student gathers information from a random sample of male and female students on campus. The amount of time spent working out is normally distributed. The data are given below.



-What statistical test should be used to analyze these data?

Question 20

A college student is interested in whether there is a difference between male and female students in the amount of time spent working out each week. The student gathers information from a random sample of male and female students on campus. The amount of time spent working out is normally distributed. The data are given below.



-Identify H₀ and Ha for this study.

Question 21

A college student is interested in whether there is a difference between male and female students in the amount of time spent working out each week. The student gathers information from a random sample of male and female students on campus. The amount of time spent working out is normally distributed. The data are given below.



-Conduct the appropriate analysis.

Question 22

A college student is interested in whether there is a difference between male and female students in the amount of time spent working out each week. The student gathers information from a random sample of male and female students on campus. The amount of time spent working out is normally distributed. The data are given below.



-Should H₀ be rejected? What should the researcher conclude?

Question 23

A college student is interested in whether there is a difference between male and female students in the amount of time spent working out each week. The student gathers information from a random sample of male and female students on campus. The amount of time spent working out is normally distributed. The data are given below.



-If significant, compute the effect size and interpret this.

Question 24

A college student is interested in whether there is a difference between male and female students in the amount of time spent working out each week. The student gathers information from a random sample of male and female students on campus. The amount of time spent working out is normally distributed. The data are given below.



-If significant, draw a graph representing the data.

Question 25

A college student is interested in whether there is a difference between male and female students in the amount of time spent working out each week. The student gathers information from a random sample of male and female students on campus. The amount of time spent working out is normally distributed. The data are given below.



-Calculate the 95% CI.

Question 26

A student is interested in whether students who study with others devote as much attention to their studies as do students who study alone. He believes those who study alone devote more attention to their studies. He randomly assigns subjects to either group or individual study conditions and has them read and study the same passage of information for the same amount of time. Subjects are then all given the same 10-item test on the material. Their scores appear below. Scores on the test represent interval/ratio data and are normally distributed.



-What statistical test should be used to analyze these data?

Question 27

A student is interested in whether students who study with others devote as much attention to their studies as do students who study alone. He believes those who study alone devote more attention to their studies. He randomly assigns subjects to either group or individual study conditions and has them read and study the same passage of information for the same amount of time. Subjects are then all given the same 10-item test on the material. Their scores appear below. Scores on the test represent interval/ratio data and are normally distributed.



-Identify H₀ and Ha for this study.

Question 28

A student is interested in whether students who study with others devote as much attention to their studies as do students who study alone. He believes those who study alone devote more attention to their studies. He randomly assigns subjects to either group or individual study conditions and has them read and study the same passage of information for the same amount of time. Subjects are then all given the same 10-item test on the material. Their scores appear below. Scores on the test represent interval/ratio data and are normally distributed.



-Conduct the appropriate analysis.

Question 29

A student is interested in whether students who study with others devote as much attention to their studies as do students who study alone. He believes those who study alone devote more attention to their studies. He randomly assigns subjects to either group or individual study conditions and has them read and study the same passage of information for the same amount of time. Subjects are then all given the same 10-item test on the material. Their scores appear below. Scores on the test represent interval/ratio data and are normally distributed.



-Should H₀ be rejected? What should the researcher conclude?

Question 30

A student is interested in whether students who study with others devote as much attention to their studies as do students who study alone. He believes those who study alone devote more attention to their studies. He randomly assigns subjects to either group or individual study conditions and has them read and study the same passage of information for the same amount of time. Subjects are then all given the same 10-item test on the material. Their scores appear below. Scores on the test represent interval/ratio data and are normally distributed.



-If significant, compute the effect size and interpret this.

Question 31

A student is interested in whether students who study with others devote as much attention to their studies as do students who study alone. He believes those who study alone devote more attention to their studies. He randomly assigns subjects to either group or individual study conditions and has them read and study the same passage of information for the same amount of time. Subjects are then all given the same 10-item test on the material. Their scores appear below. Scores on the test represent interval/ratio data and are normally distributed.



-If significant, draw a graph representing the data.

Question 32

A student is interested in whether students who study with others devote as much attention to their studies as do students who study alone. He believes those who study alone devote more attention to their studies. He randomly assigns subjects to either group or individual study conditions and has them read and study the same passage of information for the same amount of time. Subjects are then all given the same 10-item test on the material. Their scores appear below. Scores on the test represent interval/ratio data and are normally distributed.



-Calculate the 95% CI.