Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
A researcher takes a random sample of adults, without replacement, in a made-up town of adults, where the true share who own a bicycle is . A colleague takes a random sample of in a country of million adults with the same true share. When the sample is a large part of the population, the standard error is multiplied by a correction factor , where is the population size. Find the standard error from the formula . Find the correction factor for the town. Find the corrected standard error for the town. Find the correction factor for the country. Give all answers to four decimal places.
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. The formula. .
Step 2. The town. .
Step 3. Corrected. .
Step 4. The country. , which is to four places.
Answer: , , and .
What it means. Even in the town, where the sample is of the adults, the correction is only about . In the country it is nothing. The sample size, not the population size, sets the precision.
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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.