How does standard deviation std work?

ok, if a class is curved.....how does the standard deviation work? say, the std is 7.5, so does that mean 7.5 points above or below the average is C- and C+


please, someone who understands, let me know thnx!

How does standard deviation std work?
ok what is the mean score of the Test.


Lets say the Mean score is 50


The standard d is 7.5.


The +1 SD = 57.5


The -1 SD = 43.5


the scores that fall in that range make up scores of 68% of the students who took that test.


If you need more help email me. I am a teacher who has a masters in assessment. my email is the same as my yahoo ID


Good luck
Reply:itsgood2b is correct in describing the characteristics of the normal distribution, but your question seems to ask what the relationship is between the distribution and corresponding letter grades.





The determination of letter grades from the score distribution is arbitrary, but not capricious. Your teacher may assign grades as he or she sees fit.





One such scheme is to assign an A to scores 1 SD above Mean, a B from the Mean to +1 SD, a C from the Mean to -1 SD, a D from -1 SD to -2 SD, and an F below that. As you can tell, the teacher can be a "hard" or "easy" grader by selecting where the grades match the scores.





Since you will be discussing the above question with your teacher, be sure to ask about item analysis for the test. Best wishes.

gerbera