Hey Forum members. I was solving the quiz mentioned above and noticed that the answer for question 3 of the quiz, asking for the population standard deviation of 10, 25, 20 & 26 is said to be 7, and my answer of 6 is incorrect. I re-checked my calculations and sure enough, I found that the population standard deviation = 6 whereas the sample standard deviation = 7 (all values are rounded to the nearest integer). Request “Leaderboard” to please correct the answer key for all future quiz-takers.
Apologies, this has been fixed (also: there is no need to quote me - I’m not the only staff member who can make this fix).
Sorry for that, have noted for future posts. Thanks for the info 
won’t the sample standard deviation be 8 though? I’m getting the value after taking the square root of : 181/3 as 7.7674535, which will round off to 8?
Share your steps.
rearrange the list to : 10, 20, 25, 26
mean → 22.5
= (22.5-10)^2 + (22.5-20)^2 + (25-22.5)^2 + (26-22.5)^2 / 3
= [156.25 + 6.25 + 6.25 + 12.25] / 3
= 181/3
= 60.33333
= square root(60.333…) = 7.767
~ 8
Your mean isn’t right.