A town's January high temperatures average 36°F with a standard deviation of 10°, while in July the mean high temperature is 74° and the standard deviation is 8°. In which month is it more unusual to have a day with a high temperature of 55°?

1 Answer

July

Explanation:

Find and compare the z-scores of January and July. The z-score formula is:
z=(x-mu)/sigma

January:
z=(55-36)/10=1.9

July:
z=(55-74)/8=-2.375

Since the z-score for July is 2.375 standard deviations away from its mean, it is more unusual to have a high temperature of 55 degrees.