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**The applied knowledge of statistics**

「Yes」・・・8

「No」・・250

168cm 190cm 193cm 174cm 178cm

Tree１ | Tree２ | Tree３ | Tree４ | Tree５ | Average | Variance | Standard deviation | |

Thickness | 22 | 27 | 29 | 19 | 33 | 26 | 24.8 | √24.8 |

Height | 13 | 15 | 18 | 14 | 20 | 16 | 6.8 | √6.8 |

The covariance of the data is

{(22-26)(13-16)+(27-26)(15-16)+(29-26)(18-16)+(19-26)(14-16)+(33-26)(20-16)}÷5=59÷5=11.8

Correlation coefficient(=r) is certainly -1≦r≦1. It has three features.

(1)If r is near 1, it is called strong positive correlation.

The biggger one data become, the bigger another data become.

(2)If r is near 0, it has no relationship between of two data.

(3)If r is near -1, it is called strong negative correlation.

The smaller one data become, the smaller another data become.

r=11.8÷(√24.8√6.8)≒0.91

So, the thickness of tree and the height of tree has strong positive correlation