# Margin of Error & Sample size

8. Suppose that it is a presidential election year and Ohio is one of the 'swing' states. Your polling company wants to conduct a presidential preference poll of the citizens of Ohio to predict which candidate will win the election.

a. How many voters must be polled to be 95% confident of your results within +/- 3%?

b. How many voters must be polled to be 95% confident of your results within +/- 2%?

c. How many voters must be polled to be 95% confident of your results within +/- 1%?

d. Discuss the effect of margin of error on sample size.

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PROBABILITY

8. Suppose that it is a presidential election year and Ohio is one of the â€œswingâ€ states. Your polling company wants to conduct a presidential preference poll of the citizens of Ohio to predict which candidate will win the election.

Answers

The sample size is given by where p is taken as 0.5

a. How many voters must be polled to be 95% confident of your results within +/- 3%?

Given that E = 3% = 0.03, = 1.959963985

Therefore, ...

#### Solution Summary

The solution provides step by step method for the calculation of margin of error and sample size. Formula for the calculation and Interpretations of the results are also included.