Ch. 7 



LINEAR REGRESSION AND CORRELATION 



193 



the points on the graph. The amounts by which the monthly mean 

 temperatures are above or below the mean of all the temperatures 

 are shown as vertical distances above or below the horizontal line. 



90 



80 



g 70 - 



g.60 



E 



<L> 



>"50 

 40 



30 



63.8 C 



2 3 4 5 



Order of draw 

 A 



May 



July 



Apr. 



Month 



B 



Figure 7.01. Mean monthly temperatures at Topeka, Kansas, plotted first at 

 random and then according to the corresponding month. 



As far as Figure 7.01A is concerned these deviations are simply the 

 consequences of unexplained variations in temperature. However, 

 when each temperature is associated with the month to which it 

 belongs (as in Figure 7.015) it is apparent that all but a small 

 amount of the variability among these temperatures is associated 

 with a definite tendency to increase rather uniformly with succeed- 

 ing months of the season. 



