"Thirty percent of U.S. adults say they prefer cats" .
a. random sample of size n=20 US adults is selected . find the mean and the standard deviation of the distribution of sample proportions according to the Central Limit Theorem for proportions.
b. random sample of size n=200 US adults is selected.find mean and the standard deviation of the distribution of sample proportions according to the Central Limit Theorem for proportions.
c. in either a or b, is the distribution of sample proportions to be closer to a Normal approximation and why?
a)
Mean = = 0.30
Standard deviation = sqrt[ ( 1 - ) / n] = sqrt [ 0.3 * ( 1 - 03) / 20] = 0.1025
b)
Mean = = 0.30
Standard deviation = sqrt[ ( 1 - ) / n] = sqrt [ 0.3 * ( 1 - 03) / 200] = 0.0324
c)
Since sample size for b is sufficiently large and both conditions
n >= 10 and n ( 1 - ) >= 10 for part b.
For b, the distribution of sample proportions to be closer to a Normal approximation
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