# Math Help - finding sample variance

1. ## finding sample variance

having trouble identifying what is what, and alpha is confusing me. thank you

A random sample of 100 observations was drawn from a normal population. The sample variance was calculated to be 220. Test with alpha = .05 to determine whether we can infer that the population variance differs from 300.

2. $H_o: \sigma^2=300$ vs. $H_a: \sigma^2\ne 300$

The test statistic is ${(n-1)s^2\over \sigma_o^2}={(99)(220)\over 300}$

NEXT split your alpha in half and put .025 into each tail of a chi-square with 99 dfs.

You can use the table at http://www.danielsoper.com/statcalc/calc12.aspx
if you can't find one with 99 dfs.