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

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- May 5th 2010, 03:18 PMMistiniNormal Distributions
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 - May 5th 2010, 05:09 PMmatheagle
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