My last problem for the day ^_^
Suppose X=SAT score and X~N(1020,?). Suppose we take a SRS of 16 SAT scores and find s=100. Find P(xbar<950).
Answer choices:
A) 950
B) .7527
C) .9933
D) .0067
E) 0
F) .2473
Use a t with 15 dfs.
$\displaystyle P(\bar X<950)=P\left( {\bar X-\mu\over s/\sqrt{n}} < {950-1020\over 100/4}\right)$
$\displaystyle P(t_{15}<-2.8)=.006730$
from http://www.danielsoper.com/statcalc/calc08.aspx