Posted by **Anonymous** on Saturday, November 3, 2012 at 9:40pm.

The average age for licensed drivers in the county

is μ 40.3 years with a standard deviation of

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. 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 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?

- statistics -
**PsyDAG **, Sunday, November 4, 2012 at 1:27pm
Z = (mean1 - mean2)/standard error (SE) of difference between means

SEdiff = √(SEmean1^2 + SEmean2^2)

SEm = SD/√n

If only one SD is provided, you can use just that to determine SEdiff.

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

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