SOLUTION: According to Gallup's poll on consumer behavior, 36% of Americans say they will consider only cars manufactured by an American company when purchasing a new car. If you select a ra

Question 905438: According to Gallup's poll on consumer behavior, 36% of Americans say they will consider only cars manufactured by an American company when purchasing a new car. If you select a random sample of 200 Americans,
a. what is the probability that the sample will have between 30% and 40% who say they will consider only cars manufactured by an American company when purchasing a new car?
b. the probability is 90% that the sample percentage will be contained within what symmetrical limits of the population percentage?
c. the probability is 95% that the sample percentage will be contained within what symmetrical limits of the population percentage?
Please help with showing the work and excel formulas if possible. Thank you so much,
Answer by ewatrrr(24785) (Show Source): You can put this solution on YOUR website!
a)
z= (.30-.36)/sqrt[ .36*.64/200] = -.06/.0339 = -1.7699
z = (.40-.36)/sqrt[ .36*.64/200] = .04/.0339 = 1.1799
P(.30 < x-bar > .40) = NORMSDIST(1.1799) - NORMSDIST(-1.7699)
b)z = NORMINV(.95) = (X-.36)/.0039
.0039NORMSINV(.95) + .36 = upper bound
.0039NORMSINV(.05) + .36 = lower bound
c)
.0039NORMSINV(.925) + .36 = upper bound
.0039NORMSINV(.025) + .36 = lower bound
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