00:01
All right, so for this problem, i'm going to be using excel just as a fancy calculator effectively, so you can follow along with the steps even if you're just calculating out everything by hand.
00:10
So the first step that we need to take here is to find the difference between each individual rating by consumer.
00:19
So of course we can see for consumer 1, the difference would simply be 0 because 5 minus 5.
00:24
For consumer 2, it's 7 minus 9 for a difference of negative 2 and so on.
00:30
So we can see that these are going to be our individual differences.
00:34
For calculating the mean value of the difference, the first thing that we want to do is find the sum of the differences.
00:42
So we do that just by, well, adding them all up.
00:45
So we do 0 minus 2, minus 2, minus 3, plus 0, plus 1, minus 1, minus 1.
00:52
We get that the sum is negative 8.
00:55
The mean value is then going to be the sum divided by the number of values.
01:02
So negative 8 over 8 gives us a mean value of negative 1.
01:05
Then we'll also want to go through and calculate out for each one of the consumers the difference minus the mean difference.
01:18
So for instance, we would have for the first consumer that's 0 minus negative 1, that's going to be positive 1, then negative 2 minus negative 1, that's going to give us a value of positive 1.
01:33
Or, pardon me, that's, yeah, that is a value of positive 1.
01:37
And wait a second, i just realized i'm referencing these wrong.
01:40
One second here.
01:45
So actually, it should be negative 1 as the difference between the individual value, or between the individual difference and the mean.
01:52
Then from that we want to then find the deviations squared.
02:00
So we just take the difference between the individual difference in the mean value and square it.
02:06
We do this because we have that the standard deviation going to be the square root of one over the sample size, or one over the sample size minus one rather, so square root of one over seven times the sum of those squared deviations.
02:25
So our standard deviation is roughly 1 .309.
02:31
Now that we have that, we have that the null hypothesis for our hypothesis test here is going to be that the population mean difference is equal to zero...