What does standard deviation mean in here?

If a certain sample of data has a mean of 20.0 and a standard deviation of 3.0 , which of the following values is more than 2.5 standard deviations from the mean?





a. 12


b. 13.5


c. 17


d. 23.5


e. 26.5

What does standard deviation mean in here?
The mean of what? It really depends on the sample size, statistically, a certain number people will will answer a certain way at random, that's what a standard deviation is.


Just from the info you gave, a value that is 7 higher or 7 lower would be your answer, but it has to be more than 7 (more than 2.5 sd from the mean of twenty, so at least 8) the only answer that fits is ..............a.12.
Reply:2.5 standard deviations would be ±8.5 from 20. The low would be 11.5 and the high would be 28.5. Therefore, none of these would be more than 2.5 standard deviations from the mean.
Reply:This problem is asking you to find the value that is greater than 2.5 standard deviations (std) from the mean.





They tell you that one std = 3.0. So, 2.5 std = 2.5 * 3.0 = 7.5





So, you're looking for the value that is more than 7.5 units higher or lower than the mean, 20. This translates to a value greater than 27.5 or less than 12.5.





Answer a. fits that description.