Practice Quiz 1 and Quiz 1

I decided to post the questions and answers here, so it is available to all students:

Q. A researcher would like to estimate the proportion of adult voters who are in favor of Proposition A. The population of adult voters is stratified into males and females. Sixty percent of the population is known to be male. A stratified random sample of size 100 (50 males and 50 females) is taken from the population. If the sample proportion of males favoring Proposition A is 0.17, while the sample proportion of females favoring Proposition A is 0.62, then estimate the proportion of adult voters in the population favoring Proposition A. Give you answer accurate to two decimal places. For example, if your answer is 40%, state your answer as 0.40.
A. Two things to remember. First, the answer they want is the proportion in the population. Secondly, we know the proportion in the sample. We know that 0.17 of males (from the sample) prefer Proposition A. The percentage of males in the population is 0.60. Thus, of the males, 0.60 x 0.17 prefer Proposition A. Similiarly, 0.62 of females prefer Proposition A, and .40 of the population contains Females. Thus, of the females, 0.40 x 0.62 prefer Proposition A. Adding them, 0.60 x 0.17 + 0.40 x 0.62 = .35. You might have different numbers, but the logic should be the same.