00:01
All right, so for the first part of the problem here, we're asked to find the coefficient of correlation, r, which we can find by taking the sum of the ith x value minus the average of the x values, times the ith y value minus the average of the y values, divided by the square root of the sum of the ith x value minus the average x value squared, times the sum of the ith y value minus the average y value squared.
00:34
So i'll show the process of doing all these calculations using excel, but i won't use xl to find the final values.
00:43
So we want our x and y values, where we're trying to predict calories based on the number, or based on the amount of sugar.
00:52
So we have, for sugar weedies, x is four, y is 100.
00:56
For mini wheat, x is 10, y is 200.
01:01
For post -shredded wheat vanilla almond, it's 11 and 190.
01:06
For corn flakes, it's 2 and 100.
01:09
And for albrand, it's 6 and 80.
01:12
Then we need to find our averages, x bar and y bar.
01:16
So, of course, we can find an average by adding up all of the individual measurements, then dividing by the number of measurements, or alternatively, if you are using something like excel, and just use the average command, similarly for y.
01:30
So we have our average x value is 6 .6, and our average y value is 134.
01:36
So then we want to create columns for x minus x bar squared, y minus y bar squared, oops, not 62, pardon me, that should be to the power of two, and x minus x bar times y minus y bar...