SOLUTION: I'm preparing notes for final exam, want to have clear understanding of these problems, can someone help with it? Assume that a normal distribution has a mean of 25 and a standa

Question 747359: I'm preparing notes for final exam, want to have clear understanding of these problems, can someone help with it?
Assume that a normal distribution has a mean of 25 and a standard deviation of 2.5. Use the 68-95-99.7 Rule to find the percentage of values in the distribution of:
A) Above 30
B) Below 22.5
C) Between 20 and 30
D) Between 25 and 32.5
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Assume that a normal distribution has a mean of 25 and a standard deviation of 2.5. Use the 68-95-99.7 Rule to find the percentage of values in the distribution of:
A) Above 30
(30-25)/2.5 = 5/2.5 = 2
So 30 is 2 standard deviations above the mean.
Percentage above 30 = (100-95)/2 = 2.5% = 0.025
----------------------------------------------------
B) Below 22.5
(22.5-25)/2.5 = -1
So 22.5 is 1 standard deviation below the mean.
Percentage below 22.5 = (100-68)/2 = 16% = 0.16
----------------------------------------------------
Comment: Hope you can figure out "C" and "D"
C) Between 20 and 30
D) Between 25 and 32.5
------------
Cheers,
Stan H.

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