# A political candidate has asked you to conduct a poll to determine what percentage of people support her.If the candidate only wants a 3% margin of error at a 99% confidence level, what size of sample is needed?

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A political candidate has asked you to conduct a poll to determine what percentage of people support her.

If the candidate only wants a 3% margin of error at a 99% confidence level, what size of sample is needed?

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Step 1

Here, there is no information about the population parameter. Hence, use the conservative estimate π=0.5.

Step-by-step procedure to obtain the value of z using MINITAB:

• Choose Graph > Probability Distribution Plot choose View Probability > OK.
• From Distribution, choose ‘Normal’ distribution.
• Choose Probability and Both Tail for the region of the curve to shade.
• Enter the Probability value as 01.
• Click OK.

Output using the MINITAB software is given below:

Step 2

From the output, the value of z is 2.576 for 99% confidence...

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