Download Sampling Distribution of Proportions

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9.2 SAMPLE PROPORTIONS
p = population proportion
proportion of people who voted for Obama
in US
= p hat, sample proportion
proportion of people who voted for Obama
in our sample
is an unbiased estimator of p.
The sampling distribution of the sample
proportion phat has a shape that
is close to normal.
Its mean is close to the
population proportion p.
 The standard deviation of its sampling
distribution gets smaller as the size
of the sample gets larger.
The standard deviation of the
sampling distribution is
√
p(1-p)
n
Rule of Thumb 1:
Use this formula for standard
deviation of only when the
Population is at least 10 times
as large as the sample.
N > 10n
Rule of Thumb 2:
Use the normal approximation
to the sampling distribution of ê
for values of n and p that satisfy
np ≥ 10 and n(1-p) ≥ 10
Lets do #15 & 17 p.477
Assignment:
p.477 – 478 #16,18,19 - 21