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(i)

(ii)

Using the Graphing Calculator,

The product moment correlation coefficient measures the strength and direction of a linear relationship between two variables. Thus, the r-value only indicate correlation, but not causality. It is possible for the relation to be non-linear, and yet have a value close to 1. We need to look at the scatter diagram to determine whether the relationship is truly linear.

(iii)

Using

Using

Since is close to 1. We conclude that is the better model.

(iv)

Using Graphing Calculator,

When

### KS Comments:

Some students actually drew the scatter diagram for the given data, which was really strange. The meaning of r-value has to be well understood to answer (ii) well. Some actually don’t know what does least squares regression refer to.

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