the mean for math students on their final exam is 170 with a variance of 400. the teacher hypothesizes that 100 of his next students will scored better next year. here is the data the teacher has: the average points for this group=180 and the variance 400. we would like to test the hypothesis to assess if the 2 means are significantly different rom each other. what would be the calculated z? what would be the conclusion?(would you reject the null hypothesis?

Question

anonymous · Answer

Normally a test of the means would be a t-test, but if the number of samples is large, using the normal distribution, along with the standard error of the mean [standard deviation divided by 
sqrt(number of samples)] is a good approximation. There are a couple of ways to calculate the standard error of the mean, depending on whether you assume the underlying variances are identical.

anonymous · Answer

I know z is (x-u)/sd, but i dont know how to compare the two means

anonymous · Answer

yeah @douglaswinslowcooper standard deviation is sqrt root of the variance, sqrt of 400 is 20