GreenFacts, a non-profit organization, reports that the average adult in Europe consumed 17 litres of alcohol last year. The standard deviation is 2.1 litres. If we randomly select 42 European adults, what is the probability that the sample mean is more than 17.8 litres?
A) 0.0068
B) 0.4873
C) 0.0058
D) 0.4863
E) 0.0680

Question

Quizplus · Accepted Answer

The probability that the sample mean is more than 17.8 litres is 0.0068. This is because the sample mean is normally distributed with a mean of 17 litres and a standard deviation of 2.1 litres. The z-score for a sample mean of 17.8 litres is (17.8 - 17) / 2.1 = 0.38. The probability that the z-score is greater than 0.38 is 0.0068.

GreenFacts, a Non-Profit Organization, Reports That the Average Adult in Europe