StatisticsdrillSample size for a mean
A statistics problem from Statisticsdrill. Solve it with one answer box, with a fresh sample on every attempt and the worked steps and spreadsheet function in the answer, and it is checked the moment you submit.
The task
A planning study puts the standard deviation of customer spend at $34.00. How many customers must be sampled to estimate mean spend within $4.00 with 99% confidence? Use z* = 2.576. Give a whole number.
What this problem teaches
Rounding down would give a margin slightly wider than required, so sample sizes always round up.
A hint if you get stuck
n = (z* σ / E)², and always round up to the next whole person.
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