Ten Years Ago,only 20% of the U

Multiple Choice

Ten years ago,only 20% of the U.S.population consisted of people more than 65 years old.A researcher plans to use a sample of n = 200 people to determine whether the population distribution has changed during the past ten years.If a chi-square test is used to evaluate the data,what is the expected frequency for the older-than-65 category?

A) 10
B) 20
C) 40
D) 100