In: Statistics and Probability
SAT verbal scores are normally distributed with a mean of 430 and a
standard deviation of 120 (based on data from the College Board
ATP). If a sample of 35 students are selected randomly, find the
probability that the sample mean is above 470.
A.) 0.244
B.) 0.9756
C.) 0.0445
D.) 0.0244
Solution :
Given that ,
mean =
= 430
standard deviation =
= 120
n = 35
=
= 430
=
/
n = 120/
35 = 20.2837
P(
> 470 ) = 1 - P(
< 470 )
= 1 - P[(
-
) /
< (470 -430) /20.2837 ]
= 1 - P(z < 1.97 )
= 1 - 0.9721 = 0.0244
PROBABILITY = 0.0244
Probability =