1. What is the range of values that a correlation co efficient may take?
2. A graduate student in developmental psychology believes there may be a relationship between birth and 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 (after obtaining permission from the students, of course). 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

a. Construct a scatter plot of the data, plotting birth weight on the x axis and IQ on the Y-axis. Does the relationship appear to be linear?

b. Assume the relationship is linear and compute the value of pearson r. developmental

3.An educator has constructed a test for mechanical aptitude. He wants to determine how reliable the test is over two administration spaced by 1 month. A study is conducted in which 10 students are given two administrations of the test, with the second admistration being 1 month after the first. The data are given in the following table.

Student Administration 1 Administration 2

1 0 1 10

2 2 1 15

3 0 2 17

4 5 2 25

5 7 2 32

6 5 3 37

7 3 4 40

8 0 4 38

9 2 3 30

10 47 49

a.Construct a scatter plot of the paired scores.

b.Determine the value of r.

c.Would it be fair to say that this is a reliable test? Explain using r^2.

4.The director of an obesity clinic in a large north western city believes that drinking soft drinks contributes to obesity in children. To determine whether a relationship exists between these two variables, she conducts the following pilot study. Eight 12 year old volunteers are randomly selected from children attending a local junior high school. Parents of the children are asked to monitor the number of soft drinks consumed by their child over a 1 week period. The children are weighed at the end of the week and their weights converted into body mass index values. THe BMI is an common index used to measure obesity and takes into account both height and weight. An individual is considered obese if he or she has a BMI value of >30, The following data are collected.

Child Number of soft drinks BMI

1 3 20

2 1 18

3 14 32

4 7 24

5 21 35

6 5 19

7 25 38

8 9 30

a. graph a scatter plot of the data. Does the relationship appear linear?

b. Assume the relationship is linear and compute Pearson r.

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