Bookstores like education, because national data show that $71$% of college graduates have read a book in the past year, compared to $54$% of the general population age 18 and over. The data also show the nationwide average educational level to be $13$ years of schooling completed, with an SD of about $3$ years, for persons age $18$ and over. A bookstore is doing a market survey in a certain county, and takes a simple random sample of $1000$ people age $18$ and over. They find the average educational level to be $14$ years, and the SD is $5$ years.

What is the standard error?

Would it be $$\frac{3}{\sqrt{1000}} = 0.0949$$ or $$\frac{5}{\sqrt{1000}} = 0.1581$$

  • $\begingroup$ I have formatted your post. Please reviews my edits to learn how to use some mathjax as well as read the link GNU Supporter provided. $\endgroup$ – Remy Apr 7 '18 at 22:28
  • $\begingroup$ Thanks @Remy, could you please tell me which one would be right? $\endgroup$ – Dona B. Apr 7 '18 at 22:30

If you use the definition of standard error you obtain: $$ SE = \frac{\sigma_{population}}{\sqrt n}$$ What is the standard deviation of the population? Can you continue from here?

  • $\begingroup$ Thanks, I don't know which SD of the population to use, would it be 5 or 3? $\endgroup$ – Dona B. Apr 7 '18 at 22:36
  • $\begingroup$ It is 3. Because this is the result of the total data set. Try to think what the meaning is of the question. $\endgroup$ – Joe Goldiamond Apr 7 '18 at 22:42

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