SOLUTION: What is the probability of getting at least 70 shoppers in our sample of 100 preferring Brand A if the true proportion of the population who prefers Brand A is 60%? Im not n

Question 743034: What is the probability of getting at least 70 shoppers in our sample of 100
preferring Brand A if the true proportion of the population who prefers Brand A
is 60%?
Im not necessarily interested in the answer although it would be nice so I can check that the explanation is legit. Im just wondering how to do this type of question.
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
What is the probability of getting at least 70 shoppers in our sample of 100
preferring Brand A if the true proportion of the population who prefers Brand A
is 60%?
--------
p = 0.6
std = sqrt[pq/n] = sqrt[0.6*0.4/100] = sqrt(0.24)/10 = 0.049
----
z(0.7) = (0.7-0.6)/0.049 = 2.041
----
P(x >= 0.7) = P(z > 2.041) = normalcdf(2.041,100) = 0.0206
==================
Cheers,
Stan H.
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