250 



PROCEEDINGS OF THE OHIO ACADEMY OF SCIENCE. 



the yield above the normal, are far in excess when the rainfall 

 was above the normal. 



If we considered only those years when the rainfall de- 

 parted one inch or more from the normal it will be seen that 

 when it was wet the corn yield was above the normal 12 times 

 and below only once, and that when it was dry there were 13 

 poor yields and only 2 good ones. In other words when the 

 rainfall in Ohio for July is more than one inch above the normal 



Figure 3. Dot chart showing the combined effect of temperature 

 and rainfall during the 10 days following the date of blossoming of 

 corn upon the yield. Wauseon and Fulton County, Ohio. 1883 to 1912. 



the probability of a good corn crop is 92%, and when the rainfall 

 is one inch or more below the normal the probability of a good 

 corn crop is only 13%. 



THE CORRELATION COEFFICIENT (r). 



The importance of the rainfall for July in connection with 

 the yield of corn as compared with other months is made plain 

 in table 2. The two graphical methods heretofore described 



