The applied knowledge of statistics
Qualitative variable is the data that we can't calculate the average on the statistics.
Do you know bigdata?
Quantitative variable is the data that we can calculate the average on the statistics.
How tall are you?
168cm 190cm 193cm 174cm 178cm
Covariance is the product of the deviation of the two data.
The relationship between the thickness of tree and the height of tree.
The covariance of the data is
Correlation coefficient is the correlation of the two data and the covariance divided by the two standard deviations.
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.
We use the example of covariance.
So, the thickness of tree and the height of tree has strong positive correlation