probability and statistics

the average age for licensed drivers in the country is u=40.3 years with a standard deviation of o= 13.2 years.
a. a researcher obtained a random sample of n=16 parking tickets and computed an average age of m=38.9 years for the drivers. is it reasonable to conclude that this set of n=16 people is a representative sample of licensed drivers?
b. the same researcher obtained a random sample of n=36 speeding tickets and computed an average age of m=36.2 years for the drivers. compute the z-score for the sample mean and find the probability of obtaining an average age this young or younger for a random sample of licensed drivers. is it reasonable to conclude that this set of n= 36 people is a representative sample of licensed drivers?

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  1. Z = (mean1 - mean2)/standard error (SE) of difference between means

    SEdiff = √(SEmean1^2 + SEmean2^2)

    SEm = SD/√n

    Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion related to the Z score.

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