A political candidate has asked his/her assistant to conduct a poll to determine the percentage of people in the community that supports him/her. If the candidate wants a 10% margin of error at a 90% confidence level, what size of sample is needed? Be sure to round accordingly. The candidate would need to survey people in the community in order to be within a 10% margin of error at a 90% confidence level.

The size of the sample needed = 67.65

Explanation:

Given that :

The margin of error = 10% = 0.10

The confidence level = 90% = 0.90

Level of significance = 1 - 0.90 = 0.10

At ∝ = 0.10

Since the proportion of people that supported him/her is not given, we assumed p = 0.50

The margin of error formula can be expressed as:

Squaring both sides; we have:

n = 67.65

Therefore, the required sample size = 67.65

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