In: Statistics and Probability
I do not know why I keep getting this question wrong, I triple checked my work!
A distribution of values is normal with a mean of 80 and a
standard deviation of 18. From this distribution, you are drawing
samples of size 23.
Find the interval containing the middle-most 40% of sample means:
ANSWER HERE
Enter your answer using interval notation. In this
context, either inclusive or exclusive intervals would be
acceptable. Your numbers should be accurate to 1 decimal places.
Answers obtained using exact z-scores or z-scores
rounded to 3 decimal places are accepted.
I got 84.5 as my answer
Let , , n=23
Now , we want to find the interval containing the middle most 40% of the sample means.
We have , the sampling distribution of the sample mean is approximately normally distributed with mean and standard deviation
Now ,
.................(I)
From standard normal distribution table , ...............(II)
From (I) and (II) , we get ,
Therefore , (78.0,82.0) be the interval containing the middle-most 40% of sample means.