SOLUTION: Suppose we wish to obtain 95% confidence interval for proportion of teachers who believe algebra should be required for every student graduating high school. We wish to have a mar

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Question 1032526: Suppose we wish to obtain 95% confidence interval for proportion of teachers who believe algebra should be required for every student graduating high school. We wish to have a margin of error 4%. How many subjects must we sample if: a. We don't know anything about the previous proportion. b. We took a sample previously and found that 23% of teachers believe Algebra should be required. c. What is the difference between parts a and b? How and why are they different?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
Suppose we wish to obtain 95% confidence interval for proportion of teachers who believe algebra should be required for every student graduating high school. We wish to have a margin of error 4%. How many subjects must we sample if:
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a. We don't know anything about the previous proportion.
n = [1.96/0.04]^2*(1/2)^2 = 600
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b. We took a sample previously and found that 23% of teachers believe Algebra should be required.
n = [1.96/0.04]^2*0.23*0.77 = 425
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c. What is the difference between parts a and b?
Taking a sample gave you more information.
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How and why are they different?
See above.
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Cheers,
Stan H.
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