Correlations and Regressions

A graduate student in developmental psychology believes there may be a relation between birth weight and subsequent IQ. She randomly samples seven psychology majors at her university and gives them an IQ test. Next, she obtains the weight at birth of the seven majors from the appropriate hospitals. The data are shown in the following table:

Student Birth weight (lbs) IQ

1 5.8 122

2 6.5 120

3 8.0 129

4 5.9 112

5 8.5 127

6 7.2 116

7 9.0 130

  1. Construct a scatter plot of the data, plotting birth weight on the X axis and IQ on the Y axis. Does the relation appear linear?
  2. Assume the relation is linear and compute the value of Pearson r. What does this value tell you about this relationship?

2. Given the following set of paired scores from 5 subjects:

Subject 1 2 3 4 5__

Y 5 6 9 9 11

X 6 8 4 8 7__

Construct a scatter plot of the data.

Compute the value of Pearson r

Add the following paired scores from a sixth subject to the data: Y = 26, X = 25.

Construct another scatter plot, this time using the six paired scores

Compute the value of Pearson r for the six paired scores.

Is there much of a difference between your answers for part b and e? Explain the difference.

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