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A library expects that about 30% of the members of a large club read a newspaper every day…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A library expects that about of the members of a large club read a newspaper every day. It plans a random sample of members. How many members must it ask for the standard error of the sample share to be at most ? How many for a standard error of at most ?
Need a reminder? The key ideaShow
Here is the standard error of a sample share.
Four times the sample halves it. The population size hardly matters unless the sample is a large part of it.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. , so .
Step 2. For , .
Answer: members and members.
Check. , as the square root rule says.
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