Transcript Notes on Finding Sample Size

In a sample of 56 students, 32 said they plan to go to
college. Find the 92% confidence interval of the proportion
of students who plan to go to college.
Confidence Interval
Sample Size
Standard Error
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It’s the estimated standard deviation of the
statistic
E  z
2
pq
n
An article by the right to die organization gave a proportion of
physician’s who agree with their cause. I want to test their claim. I
want to be within 0.05 with 95% confidence, how many must I sample?
(Assume p = 0.5)
Why did I let p = 0.5? If proportion is not given, use p = 0.5
because it’s including the most error. (Let n = 100)
p
q
0.1
0.9
0.2
0.8
0.3
0.7
0.4
0.6
0.5
0.5
pq
n
A pollster wishes to estimate the proportion of U.S. voters who favor
capital punishment. How large a sample is needed in order to be 95%
confident that the sample proportion will not differ from the true
proportion by more than 2%?
Homework
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Worksheet