StatisticsdrillConfidence interval for a proportion
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
In a random sample of 200 customers, 35 say they used the mobile app last month. What is the lower limit of a 99% confidence interval for the population proportion? Give it as a proportion. Round to 4 decimal places.
What this problem teaches
The formula: Lower = p̂ - z* √( p̂ (1 - p̂) / n ).
A hint if you get stuck
p̂ ± z* √(p̂(1 - p̂) / n). The lower limit subtracts the margin.
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