Question 1136479: I need help solving the following question with a calculator and how to type it in
CNNBC recently reported that the mean annual cost of auto insurance is 1011 dollars. Assume the standard deviation is 250 dollars. You take a simple random sample of 95 auto insurance policies.
Find the probability that a single randomly selected value is less than 985 dollars.
P(X < 985) =
Find the probability that a sample of size n=95 is randomly selected with a mean less than 985 dollars.
P(M < 985) =
Enter your answers as numbers accurate to 4 decimal places.
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! The probability x < 985 is z<(985-1011)/250
put that value into 2nd VARS (normal CDF) and use (-6, the value you get above) that value is -26/250
You can use any number less than -6 at the left end or +6 at the right end without changing the result significantly. Some use 1E99, but that isn't required.
The value will be the probability.
For the sample, z< (985-1011)/250/sqrt(95)
Same thing, only z< -26*sqrt(95)/250 and put that in. The probability will be significantly less.
Don't use normal pdf( ever.
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