In a class of 25, one student receives a score of 100 on a test. The grades are distributed normally, with a mean of 78 and standard deviation of 5. Do you think the students score is an outlier?

Question

In a class of 25, one student receives a score of 100 on a test.  The grades are distributed normally, with a mean of 78 and standard deviation of 5. Do you think the students score is an outlier?

jim_thompson5910 · Answer

how far is the score of 100 from the mean of 78?

anonymous · Answer

22

perl · Answer

you might also want to define 'outlier'

perl · Answer

a score of 100 is how many standard deviations from the mean

jim_thompson5910 · Answer

take 22 and divide it by the standard deviation 5

22/5 = 4.4

So the z-score is 4.4. This means we are 4.4 standard deviations away from the mean. Anything beyond 3 std deviations is considered to be an outlier. So this score of 100 is definitely an outlier.

anonymous · Answer

Thanks!

jim_thompson5910 · Answer

you're welcome