Question 1

The normality assumptions behind the independent groups t test

Accepted Answer

A)  is one that we cannot get around. 
B)  diminishes in importance as the variance of the two groups increases. 
C)  is absolutely unimportant. 
D)  diminishes in importance as the sample sizes increase. 
A)  is one that we cannot get around. 
B)  diminishes in importance as the variance of the two groups increases. 
C)  is absolutely unimportant. 
D)  diminishes in importance as the sample sizes increase. D

Question 2

When the assumption of homogeneity of variance is violated, the two sample means cannot be compared with a t-test.

Accepted Answer

A) True 
 B)False  False

Question 3

Which of the following is a reason why we may NOT find a significant difference between two groups?

Accepted Answer

A)  The sample size was too small. 
B)  The true mean difference between the groups was too small. 
C)  The variability between the groups was too large. 
D)  all of the above 
A)  The sample size was too small. 
B)  The true mean difference between the groups was too small. 
C)  The variability between the groups was too large. 
D)  all of the above D

Question 4

A researcher thinks that people who drive red cars drive faster than people who drive white cars. He recorded the speed of a random sample of red and white cars on a highway. The data follow. 
   
a. What is the research hypothesis? 
b. Is a one-tail or a two-tail test more appropriate? 
c. Calculate t. 
d. Is the research hypothesis supported? Explain?

Accepted Answer

a. μ _red > μ _white b. A one-tail test is approp

Question 5

The distribution of differences between means is

Accepted Answer

A)  normally distributed for very large samples. 
B)  approaches normal as sample sizes increase. 
C)  may be nonnormal for small samples. 
D)  all of the above. 
A)  normally distributed for very large samples. 
B)  approaches normal as sample sizes increase. 
C)  may be nonnormal for small samples. 
D)  all of the above.

Question 6

A movie critic believes people linger in the theatre after a movie for longer periods following dramas than comedies. The data follow. 
   
a. What is the research hypothesis? 
b. Is a one-tail or a two-tail test more appropriate? 
c. Calculate t . 
d. Is the research hypothesis supported? Explain

Accepted Answer

a. μ _drama > μ _comedy b. A one-tail test is approp

Question 7

An important reason for using random assignment in a study with independent groups is to

Accepted Answer

A)  prevent any systematic differences between groups on extraneous variables. 
B)  be able to generalize to broader populations. 
C)  rule out competing interpretations of any differences we find. 
D)  a and c 
A)  prevent any systematic differences between groups on extraneous variables. 
B)  be able to generalize to broader populations. 
C)  rule out competing interpretations of any differences we find. 
D)  a and c

Question 8

The null hypothesis of an independent samples t test is

Accepted Answer

A)  r = 0. 
B)  m 1 > m 2. 
C)  m 1 = m 2. 
D)  m 1 ≠ m 2. 
A)  r = 0. 
B)  m 1 > m 2. 
C)  m 1 = m 2. 
D)  m 1 ≠ m 2.

Question 9

p(10 ≤ (µ1 -  µ 2) ≤  15) = .95, means that there is a 95% chance that the samples were drawn from populations that have means between 10 and 15.

Accepted Answer

A) True 
 B)False

Question 10

Given the following equation, the only difference between this and our original equation for z is:

Accepted Answer

A)  the original z required a normal distribution. 
B)  we have substituted information about differences in place of information about observations. 
C)  the equations are of the same general form. 
D)  both b) and c). 
A)  the original z required a normal distribution. 
B)  we have substituted information about differences in place of information about observations. 
C)  the equations are of the same general form. 
D)  both b) and c).

Question 11

In the previous test on the treatment of anorexia, the resulting t was -3.22, which was significant (p

Accepted Answer

A)  the family therapy condition had a mean that was reliably less than the mean of the control condition. 
B)  the family therapy condition had a mean that was reliably more than the mean of the control condition. 
C)  the family therapy condition had a mean that was unreliably less than the mean of the control condition. 
D)  the family therapy condition had a mean that was unreliably more than the mean of the control condition. 
A)  the family therapy condition had a mean that was reliably less than the mean of the control condition. 
B)  the family therapy condition had a mean that was reliably more than the mean of the control condition. 
C)  the family therapy condition had a mean that was unreliably less than the mean of the control condition. 
D)  the family therapy condition had a mean that was unreliably more than the mean of the control condition.

Question 12

Homogeneity of variance means that two samples were drawn from populations with equal variances.

Accepted Answer

A) True 
 B)False

Question 13

What statistical test is used for two independent groups?

Accepted Answer

A)  z -score 
B)  chi-square 
C)  between-subject t-test 
D)  ANOVA 
A)  z -score 
B)  chi-square 
C)  between-subject t-test 
D)  ANOVA

Question 14

Given the following data, calculate and interpret t .

Accepted Answer

t = 2.22. ( t should be calcul

Question 15

The measure of the effect size for the difference between two groups is best seen as

Accepted Answer

A)  the difference in their means. 
B)    . 
C)  the ratio of the means. 
D)  all of the above 
A)  the difference in their means. 
B)    . 
C)  the ratio of the means. 
D)  all of the above

Question 16

We would NOT pool the variances if

Accepted Answer

A)  we had too few subjects. 
B)  we had too many subjects. 
C)  The means were clearly different. 
D)  we had very unequal sample variances. 
A)  we had too few subjects. 
B)  we had too many subjects. 
C)  The means were clearly different. 
D)  we had very unequal sample variances.

Question 17

Which of the following would make you believe that you have two independent groups?

Accepted Answer

A)  Subjects were assigned to groups at random as they arrived for testing. 
B)  There are 25 subjects in Group 1 and 45 subjects in Group 2. 
C)  Every subject supplies one score. 
D)  All of the above. 
A)  Subjects were assigned to groups at random as they arrived for testing. 
B)  There are 25 subjects in Group 1 and 45 subjects in Group 2. 
C)  Every subject supplies one score. 
D)  All of the above.

Question 18

Mean scores in Tetris were recorded for both math majors and English majors. The mean score for math majors was 20,752 (s12 = 851, N1 = 17) and the mean score for English majors was 14,922 (s22 = 395, N2 = 56). The pooled variance would probably be closest to which value?

Accepted Answer

A)  800 
B)  623 
C)  500 
D)  900 
A)  800 
B)  623 
C)  500 
D)  900

Question 19

According to the variance sum law, the variance of the difference of two independent variables is equal to the difference of their variances.

Accepted Answer

A) True 
 B)False

Question 20

Normality of distributions is an assumption involved in the use of a t-test.

Accepted Answer

A) True 
 B)False

The normality assumptions behind the independent groups t test

When the assumption of homogeneity of variance is violated, the two sample means cannot be compared with a t-test.

Which of the following is a reason why we may NOT find a significant difference between two groups?

The distribution of differences between means is

A movie critic believes people linger in the theatre after a movie for longer periods following dramas than comedies. The data follow. a. What is the research hypothesis? b. Is a one-tail or a two-tail test more appropriate? c. Calculate t . d. Is the research hypothesis supported? Explain

An important reason for using random assignment in a study with independent groups is to

The null hypothesis of an independent samples t test is

p(10 ≤ (µ₁ - µ ₂) ≤ 15) = .95, means that there is a 95% chance that the samples were drawn from populations that have means between 10 and 15.

Given the following equation, the only difference between this and our original equation for z is:

In the previous test on the treatment of anorexia, the resulting t was -3.22, which was significant (p

Homogeneity of variance means that two samples were drawn from populations with equal variances.

What statistical test is used for two independent groups?

Given the following data, calculate and interpret t .

The measure of the effect size for the difference between two groups is best seen as

We would NOT pool the variances if

Which of the following would make you believe that you have two independent groups?

Mean scores in Tetris were recorded for both math majors and English majors. The mean score for math majors was 20,752 (s₁² = 851, N₁ = 17) and the mean score for English majors was 14,922 (s₂² = 395, N₂ = 56). The pooled variance would probably be closest to which value?

According to the variance sum law, the variance of the difference of two independent variables is equal to the difference of their variances.

Normality of distributions is an assumption involved in the use of a t-test.

Introduction

Basic Concepts

Displaying Data

Measures of Central Tendency

Measures of Variability

The Normal Distribution

Basic Concepts of Probability

Sampling Distributions and Hypothesis Testing

Correlation

Regression

Multiple Regression

Hypothesis Tests Applied to Means: One Sample

Hypothesis Tests Applied to Means: Two Related Samples

Power

One-Way Analysis of Variance

Factorial Analysis of Variance

Repeated-Measures Analysis of Variance

Chi-Square

Nonparametric and Resampling Statistical Tests

Meta-Analysis

Filters

Exam 14: Hypothesis Tests Applied to Means: Two Independent Samples

The normality assumptions behind the independent groups t test

When the assumption of homogeneity of variance is violated, the two sample means cannot be compared with a t-test.

Which of the following is a reason why we may NOT find a significant difference between two groups?

The distribution of differences between means is

A movie critic believes people linger in the theatre after a movie for longer periods following dramas than comedies. The data follow. a. What is the research hypothesis? b. Is a one-tail or a two-tail test more appropriate? c. Calculate t . d. Is the research hypothesis supported? Explain

An important reason for using random assignment in a study with independent groups is to

The null hypothesis of an independent samples t test is

p(10 ≤ (µ1 - µ 2) ≤ 15) = .95, means that there is a 95% chance that the samples were drawn from populations that have means between 10 and 15.

Given the following equation, the only difference between this and our original equation for z is:

In the previous test on the treatment of anorexia, the resulting t was -3.22, which was significant (p

Homogeneity of variance means that two samples were drawn from populations with equal variances.

What statistical test is used for two independent groups?

Given the following data, calculate and interpret t .

The measure of the effect size for the difference between two groups is best seen as

We would NOT pool the variances if

Which of the following would make you believe that you have two independent groups?

Mean scores in Tetris were recorded for both math majors and English majors. The mean score for math majors was 20,752 (s12 = 851, N1 = 17) and the mean score for English majors was 14,922 (s22 = 395, N2 = 56). The pooled variance would probably be closest to which value?

According to the variance sum law, the variance of the difference of two independent variables is equal to the difference of their variances.

Normality of distributions is an assumption involved in the use of a t-test.

Introduction

Basic Concepts

Displaying Data

Measures of Central Tendency

Measures of Variability

The Normal Distribution

Basic Concepts of Probability

Sampling Distributions and Hypothesis Testing

Correlation

Regression

Multiple Regression

Hypothesis Tests Applied to Means: One Sample

Hypothesis Tests Applied to Means: Two Related Samples

Power

One-Way Analysis of Variance

Factorial Analysis of Variance

Repeated-Measures Analysis of Variance

Chi-Square

Nonparametric and Resampling Statistical Tests

Meta-Analysis

Filters

p(10 ≤ (µ₁ - µ ₂) ≤ 15) = .95, means that there is a 95% chance that the samples were drawn from populations that have means between 10 and 15.

Mean scores in Tetris were recorded for both math majors and English majors. The mean score for math majors was 20,752 (s₁² = 851, N₁ = 17) and the mean score for English majors was 14,922 (s₂² = 395, N₂ = 56). The pooled variance would probably be closest to which value?