Question 1

Research has indicated that there is a curvilinear relationship between the number of drinks a person has per day and their likelihood of developing heart disease. Calculating a regular correlation coefficient on these data would likely result in
A) an artificially low value.
B) a value close to +1.00.
C) a value close to -1.00.
D) a value larger than 1.00.

Accepted Answer

A curvilinear relationship does not follow a straight line, so a regular correlation coefficient (which measures linear relationships) would not accurately capture the strength of the relationship, likely resulting in an artificially low value.

Question 2

A positive value for a correlation indicates
A) increases in one variable tend to be accompanied by increases in the second variable.
B) increases in one variable tend to be accompanied by decreases in the second variable.
C) a stronger relationship than if the correlation were negative.
D) nothing; all correlation values are positive.

Accepted Answer

A positive correlation means that as one variable increases, the other variable tends to also increase. This is the definition of a positive correlation, indicating a direct relationship between the two variables. Choices B, C, and D are incorrect interpretations of a positive correlation value.

Question 3

The absolute value of a correlation coefficient indicates the__________ of the relationship and the sign indicates the of the____________ relationship.
A) causality; magnitude
B) direction; causality
C) strength; direction
D) strength; whether or not a relationship exists

Accepted Answer

The absolute value of a correlation coefficient indicates the strength of the relationship between two variables, while the sign (positive or negative) indicates the direction of the relationship.

Question 4

For a data set with a mean = 10 and standard deviation = 2, what is the z score corresponding to a raw score of 7?
A) +1.5
B) -1.5
C) 2
D) -2

Accepted Answer

The z score is calculated as (X - mean) / standard deviation = (7 - 10) / 2 = -3 / 2 = -1.5.

Question 5

When calculating a correlation coefficient,_____________ can only be used when the data are related in a linear fashion.
A) Cohen's d
B) Pearson's correlation
C) z score
D) F test

Accepted Answer

Pearson's correlation is specifically designed to measure the strength and direction of a linear relationship between two continuous variables.

Question 6

How does multiple regression differ from simple regression?
A) it contains multiple data points
B) it involves multiple dependent variables
C) it includes multiple independent/predictor variables
D) it can always be used to establish causality

Accepted Answer

Multiple regression includes multiple independent or predictor variables, unlike simple regression, which involves only one independent variable and one dependent variable.

Question 7

An effect size is a measure of
A) the magnitude of the relationship between two variables.
B) whether the result reached statistical significance.
C) the validity of our result.
D) the probability that we made a correct decision.

Accepted Answer

An effect size specifically refers to the magnitude of the relationship between two variables, indicating how strong or meaningful that relationship is, rather than just whether it is statistically significant.

Question 8

A perfect relationship will results in a correlation coefficient value of
A) 1.00.
B) -1.00.
C) both a and b
D) neither a nor b

Accepted Answer

A perfect relationship in correlation can be either perfectly positive (1.00) or perfectly negative (-1.00), indicating a perfect linear relationship in either direction.

Question 9

Assume that the correlation coefficient between class attendance and number of problems missed on an exam is -.77). Which of the following statements regarding this finding is correct?
A) students who had fewer absences answered more questions correctly
B) students who had more absences answered more questions correctly
C) a negative correlation value is impossible; there must be a mistake in the calculations
D) the number of problems answered correctly is below the class mean

Accepted Answer

A negative correlation coefficient of -.77 indicates an inverse relationship between class attendance and the number of problems missed on an exam. This means that as class attendance increases (fewer absences), the number of problems missed decreases (more questions answered correctly).

Question 10

Which of the following is a measure of the standardized difference between two means?
A) Cohen's d
B)-bar
C) SD
D) Σr

Accepted Answer

Cohen's d is a measure of the standardized difference between two means, often used in statistics to quantify the effect size.

Question 11

Assume that within one study the regression equation relating daily saturated fat intake in grams x) to blood cholesterol level y) is Y-hat = 130 + 5X. What is the value of the y-intercept for this problem?
A) 1
B) 5
C) 130
D) impossible to determine

Accepted Answer

The y-intercept in a regression equation is the value of Y when X is 0. In the given equation, Y-hat = 130 + 5X, the y-intercept is 130, which corresponds to the constant term in the equation.

Question 12

In a normal distribution, the percentage of raw scores falling within one standard deviation of the mean equals
A) 34.11%.
B) 68.26%.
C) 95.44%.
D) 99.74%.

Accepted Answer

In a normal distribution, approximately 68.26% of the data falls within one standard deviation of the mean. This is a fundamental property of normal distributions.

Question 13

What position in a distribution of numbers corresponds to a z score of z = -2.00?
A) two standard deviation units above the mean
B) two points above the mean
C) two standard deviation units below the mean
D) two points below the mean

Accepted Answer

A z score of z = -2.00 indicates a position two standard deviation units below the mean in a distribution.

Question 14

What is the median of these numbers: 2, 7, 6, 8, 10 ?
A) 7
B) 6
C) 8
D) 10

Accepted Answer

First, arrange the numbers in ascending order: 2, 6, 7, 8, 10. The median is the middle number, which is 7.

Question 15

The amount of change in Y for every one unit increase in X is indicated by the
A) magnitude of the correlation coefficient.
B) correlation coefficient sign.
C) y-intercept.
D) slope regression coefficient).

Accepted Answer

The slope of the regression coefficient directly measures the change in the dependent variable (Y) for a one-unit increase in the independent variable (X), making it the correct answer.

Question 16

Vanessa Kanaan, an Associate Professor at the University of Louisville, creates a new "empathy" test and administers it to business majors and biology majors. She finds that the two groups differ significantly from each other with an effect size Cohen's d) equal to .85. Based on this information which of the following statements is accurate?
A) although her results are statistically significant, the effect size would be considered "small" meaning that it has little practical importance
B) the effect size in this study would be considered "moderate"
C) the effect size in this study would be considered "large"
D) it is impossible to obtain an effect size of .85; she must have calculated it incorrectly

Accepted Answer

Cohen's d is a measure of effect size used to indicate the standardized difference between two means. A value of .85 is considered "large" according to conventional benchmarks, suggesting a substantial difference between the two groups.

Question 17

The normal distribution follows within rounding) which of the following rules?
A) the symmetrical rule
B) the central limit theorem
C) the 68, 95, 99.7 rule
D) the normal distribution rule

Accepted Answer

The 68, 95, 99.7 rule, also known as the empirical rule, describes how data is distributed in a normal distribution: about 68% of data falls within one standard deviation, 95% within two, and 99.7% within three.

Question 18

Dr. Wilson conducts an experiment and finds that the difference between the experimental and control group means is 45.3 units. This can be referred to as the
A) effect size indicator
B) unstandardized difference between means
C) standardized difference between means
D) z score

Accepted Answer

The difference between the experimental and control group means, expressed in the units of the dependent variable, is referred to as the unstandardized difference between means. This measure directly reflects the magnitude of the effect of the independent variable on the dependent variable without standardization.

Question 19

Professor Ganji jokes that there is a -.85 correlation between the number of courses a student takes with him and the student's grade point average. Which of the following is the best interpretation of this statement?
A) in general, the more courses that students take from professor Ganji the lower their grade point average
B) the more courses students take from professor Ganji the higher their grade point average
C) professor Ganji is an easy instructor
D) students who take more of professor Ganji's class are guaranteed to have a higher grade point average

Accepted Answer

A negative correlation (in this case, -.85) indicates that as one variable increases, the other decreases. Therefore, the more courses students take with Professor Ganji, the lower their grade point average tends to be.

Question 20

Which correlation coefficient represents the strongest association between X and Y?
A) +.20
B) +.60
C) -.80
D) -1.5

Accepted Answer

C) -.80 represents the strongest association because correlation coefficients range from -1 to +1, where -1 indicates a perfect negative linear relationship, +1 indicates a perfect positive linear relationship, and values closer to -1 or +1 indicate stronger associations. -1.5 is not a valid correlation coefficient.

Quiz 14: Descriptive Statistics

Research has indicated that there is a curvilinear relationship between the number of drinks a person has per day and their likelihood of developing heart disease. Calculating a regular correlation coefficient on these data would likely result in

A positive value for a correlation indicates

The absolute value of a correlation coefficient indicates the of the relationship and the sign indicates the of the__ relationship.

For a data set with a mean = 10 and standard deviation = 2, what is the z score corresponding to a raw score of 7?

When calculating a correlation coefficient,_____________ can only be used when the data are related in a linear fashion.

How does multiple regression differ from simple regression?

An effect size is a measure of

A perfect relationship will results in a correlation coefficient value of

Assume that the correlation coefficient between class attendance and number of problems missed on an exam is -.77) . Which of the following statements regarding this finding is correct?

Which of the following is a measure of the standardized difference between two means?

Assume that within one study the regression equation relating daily saturated fat intake in grams x) to blood cholesterol level y) is Y-hat = 130 + 5X. What is the value of the y-intercept for this problem?

In a normal distribution, the percentage of raw scores falling within one standard deviation of the mean equals

What position in a distribution of numbers corresponds to a z score of z = -2.00?

What is the median of these numbers: 2, 7, 6, 8, 10 ?

The amount of change in Y for every one unit increase in X is indicated by the

The normal distribution follows within rounding) which of the following rules?

Dr. Wilson conducts an experiment and finds that the difference between the experimental and control group means is 45.3 units. This can be referred to as the

Professor Ganji jokes that there is a -.85 correlation between the number of courses a student takes with him and the student's grade point average. Which of the following is the best interpretation of this statement?

Which correlation coefficient represents the strongest association between X and Y?