Correlation and Regression Analysis
Showing posts with label Correlation and Regression Analysis. Show all posts
Showing posts with label Correlation and Regression Analysis. Show all posts

What does 1 - r^2 measure?

What does 1 - r^2 measure?



a. The relative importance of all other possible predictor variables on y.
b. The percentage of points that are on the regression line.
c. The percentage of points that are off the regression line



Answer: a. The relative importCorrelation and Regression Analysisance of all other possible predictor variables on y.

Which of the following statements is not correct regarding the correlation.

Which of the following statements is not correct regarding the correlation.



a. It can range from -1 to 1.
b. Its square is the percentage of variance accounted for.
c. It measures the percent of variation explained.
d. It is a measure of the association between two variables


Answer: c. It measures the percent of variation explained.

The primary purpose of a regression equation is to

The primary purpose of a regression equation is to




a. measure the association between two variables.
b. estimate the value of the dependent variable based on the independent variable.
c. estimate the value of the independent variable based on the dependent variable.
d. estimate the percentage of variance accounted for.


Answer: b. estimate the value of the dependent variable based on the independent variable.

The ratio of SS(Regression) divided by the SS(Total) is also called the

The ratio of SS(Regression) divided by the SS(Total) is also called the




a. sum of squares due to regression
b. percentage of variance accounted for
c. standard error
d. coefficient of correlation.


Answer: b. percentage of variance accounted for

The percentage of variance accounted for

The percentage of variance accounted for




a. is the square of the coefficient of correlation.
b. cannot be negative.
c. gives the percent of the variation in the dependent variable explained by the independent variable.
d. all of the above


Answer: b. cannot be negative.

The standard error is

The standard error is



a. computed from squared deviations from the regression line.
b. may be negative
c. is given in squared units of the independent variable.
d. all of the above


Answer: a. computed from squared deviations from the regression line.

A regression equation is used to predict women's Weight (in pounds) from their Height (in inches). The correlation between Weight (W) and Height (H) turned out to be 0.70 . The average H was 64 inches and the average W was 119.6 pounds.

A regression equation is used to predict women's Weight (in pounds) from their Height (in inches). The correlation between Weight (W) and Height (H) turned out to be 0.70 . The average H was 64 inches and the average W was 119.6 pounds.


The regression equation turned out to be:

W(hat) = 30 + 1.4H

Now consider the regression equation to predict H from W using the same data set:

H(hat) = int + slope * W

where "int" and "slope" are some numbers. Find the value of "slope".



a. 0.00
b. 0.35
c. 0.55
d. 0.25
e. 0.71


Answer: b. 0.35

What is the formula for the correlation coefficient in terms of the cov?

The covariance, denoted cov, is computed from:

cov = 1/(n-1) * [E](X - X(bar))(Y - Y(bar))

What is the formula for the correlation coefficient in terms of the cov?




a. cov / s(subx)
b. cov / (s(subx) * s(suby))
c. cov / s(subx)^2
d. cov / s(suby)^2
e. (s(suby) / s(subx)) * cov


Answer: b. cov / (s(subx) * s(suby))

The coefficient of correlation was computed to be -0.60. This means

The coefficient of correlation was computed to be -0.60. This means



a. the slope and intercept of the regression line are both negative
b. as x increases, y decreases.
c. x and y are both 0.
d. the percentage of variance accounted for equals sqrt(0.6)


Answer: b. as x increases, y decreases.

We obtained the following regression equation: y(hat) = 3.5 + 2.1x.. Which of the following statements are correct?

We obtained the following regression equation: y(hat) = 3.5 + 2.1x.. Which of the following statements are correct?




a. The dependent variable is predicted to increase by 2.1 for each increase of 1 unit in X.
b. The equation crosses the y-axis at 3.5.
c. If x = 5, then y = 14.
d. if x = 5 then =14
e. (a), (b) and (d) only


Answer: e. (a), (b) and (d) only

The coefficient of correlation.

The coefficient of correlation.




a. Has the same sign as the slope
b. Can range from -1.00 to 1.00
c. Is also called the percentage of variance accounted for.
d. (a) and (b) only
e. none of the above


Answer: d. (a) and (b) only

Find the intercept and slope of the regression line to predict Y from X.

Given the following information: r = 0.60
Mean Standard Deviation
X 40 4

Y 45 6
Find the intercept and slope of the regression line to predict Y from X.




a. intercept=9.0 slope=0.9
b. intercept=0.9 slope=9.0
c. intercept=9.0 slope=9.0
d. intercept=0.9 slope=0.9


Answer: a. intercept=9.0 slope=0.9

If all the points are on the regression line, then

If all the points are on the regression line, then



a. the value of the slope is 0.
b. the value of the intercept is 0.
c. the correlation coefficient is 0.
d. the standard error is 0.
e. both (c) and (d)


Answer: d. the standard error is 0.

A correlation of 0.02 would indicate:

A correlation of 0.02 would indicate:



a. a very strong direct relationship
b. a very weak direct relationship
c. a very strong inverse relationship
d. a very weak inverse relationship
e. a computational error had been made.


Answer: b. a very weak direct relationship
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