4. The heights, \(h \mathrm {~m}\), of eight children were measured, giving the following values of \(h\) :
$$1 \cdot 20,1 \cdot 12,1 \cdot 43,0 \cdot 98,1 \cdot 31,1 \cdot 26,1 \cdot 02,1 \cdot 41$$
- Find the mean height of the children.
- Calculate the variance of the heights.
The children were also weighed. It was found that their masses, \(w \mathrm {~kg}\), were such that
$$\sum w = 324 , \quad \sum w ^ { 2 } = 13532 , \quad \sum w h = 403 .$$
- Calculate the product-moment correlation coefficient between \(w\) and \(h\).
- Comment briefly on the value you have obtained.