You can put this solution on YOUR website! FINDING SAMPLE SIZE.
Q1. margin of error:$125, confidence level:95%,standard deviation=$500
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E=z*(sigma/sqrt(n))
sqrt(n) = z*(sigma)/E
sqrt(n) = 1.96(500)/125
sqrt(n) = 7.84
n=61 (rounded to whole number)
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Cheers,
Stan H.