Catherine Chao, Director of Marketing Research, needs a sample of Ottawa households to participate in the testing of a new toothpaste package.If 40% of the households in Ottawa prefer the new package, the probability that Catherine's random sample of 300 households will have a sample proportion between 0.35 and 0.45 is ___.
A)0.9232
B)0.0768
C)0.4616
D)0.0384
E)0.8976

Question

Quizplus · Accepted Answer

The sample proportion follows a normal distribution with mean 0.40 and standard deviation sqrt[(0.40)(0.60)/300]. Using the standard normal distribution, the probability of the sample proportion being between 0.35 and 0.45 is approximately 0.9232.

Catherine Chao, Director of Marketing Research, Needs a Sample of Ottawa