I was referencing that the random sample means were larger than full sample mean:
2012: 2.42 > 2.33
2013: 2.43 > 2.35
2014: 2.51 > 2.43
2015: 2.70 > 2.62
I was referencing that the random sample means were larger than full sample mean:
2012: 2.42 > 2.33
2013: 2.43 > 2.35
2014: 2.51 > 2.43
2015: 2.70 > 2.62
Stop cowardice, ban guns!
First I thought that this is a typical homework. And I thought that it was supposed to be solved in the following way:
1) do the t-test for for the difference of the GPA scores for each of the years. (What rogojel did above.) Then the standard error will be known (or at least estimated) and thus the variances of these differences.
2) what is the sum of these differences over the 4 years? And what is the variance of that sum? (The variance of the sum is the sum of the variances. (I assume that they can be assumed to have zero correlation.)
3) What is the mean of that sum (divide it by 4) and what is the variance of that overall mean. Then you will have the t-test for the overall mean.
A little bit interesting is that I have no intuition if this will be significant or not. Although I have some experience as a statistician.
Show us the result!
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