Example 1: Review Key Concepts Unit 3 Pg 212 # 2.

A survey of a group of randomly selected students compared the number of hours of TV they watched per week with their grade averages.

a) Create a scatter plot for these data. Classify the linear correlation.
b) Determine the correlation coefficient.
c) Can you make any conclusions about the effect that watching TV has on academic achievement? Explain.

Solution

- Step 1: Draw the table and fill in the values

Hours Per Week	Grade Average %
12	70
10	85
5	82
3	88
15	65
16	75
8	68

a)
- Step 2: Create a scatter plot using the above values.




b)
r = -0.651, therefore there is a moderate negative linear correlation.

a = -1.196

b = 87.932

c) No, because according to the correlation coefficient the correlation is moderate, so it cannot be exactly considered that watching TV has direct impact on the grades.

References
Example taken from Mathematics of Data Management, McGraw-Hill Ryerson.