Regression
(A worked Problem:  This procedure is explained in Chapter 9)

Suppose that the height of an individual is correlated with her reaction time to a light flash.  In general shorter people tend to be faster than teller people.  The data that you will need for this problem are below:

Height:    Mean =66 inches             Standard Deviation = 4 inches

Reaction Time:     Mean = 300 milliseconds        Standard Deviation = 60 milliseconds

The correlation coefficient between height and reaction time = .65

1.  Predict the reaction time of a person who is 65 inches tall.

2.  Predict the height of a person who has a reaction time of 320 milliseconds.

1.

Before we begin the problem we must determine which variable we will call Y and which variable we will call X.
For this problem I will call Height "X" and I will call Reaction Time "Y."

Therefore:

I.  Predict the reaction time of a person who is 65 inches tall.
    A.  Predict Y if X = 65

    B.  Compute the standard error of the estimate for predicting Y given that you have an X.

    C.  We predict that:

Hint:  Remember that all predictions must be accompanied by the standard error of the estimate.
            A prediction without the standard error of the estimate is wrong!

2.

Before we begin the problem we must determine which variable we will call Y and which variable we will call X.
For this problem I will call Height "X" and I will call Reaction Time "Y."

Therefore:

II.  Predict the height of a person who has a reaction time of 320 milliseconds
    A.  Predict X if Y = 320

    B.  Compute the standard error of the estimate for predicting X given that you have a Y.

    C.  We predict that:

Hint:  Remember that all predictions must be accompanied by the standard error of the estimate.
            A prediction without the standard error of the estimate is wrong!

Copyright © 2004 by Mark W. Vernoy