Question 1076937: Individual scores on a 400-point standardized test had a Normal distribution with mean μ=204 and standard deviation σ=56.
(a) What percent of individual scores were higher than 213?
I got .5683
(b) The average scores for all groups of size 85 have a mean of
(c) The average scores for all groups of size 85 have a standard deviation of
(d) What percent of groups of size 85 have an average score higher than 213?
I don't understand the last 3
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! z>(213-204)/56=0.4362; it has to be < 0.5 because the scores concerned are all greater than the mean.
================
204, mean doesn't change
6.074, sd changes with the sqrt (n)
The sampling distribution has a normal distribution with the same mean as the population mean and a standard deviation sigma/sqrt (n). This says that while a single observation can be 2 sd from the mean, it is much less likely that the mean of 10 observations will be 2 sd from the mean, quantifying how far it can be.
===============
z>(9/6.074)>1.480
probability is 0.0692
|
|
|
