Need help manually finding the standard deviation using an external function
29 views (last 30 days)
Show older comments
I am new to matlab (taking an intro to matlab class), but for my assignment I have to do a number of things including randomly generating 10 scores for each of 25 students. Then take the median, mean, and standard deviation for each student's scores. For median and mean I used median(Score,2) and mean(Score,2) to find the values for each row (individual student's 10 scores). I am struggling to figure out how to manually find the standard deviation for each student. I also have to use Matlab functions to find the std and compare it to the manual calculation. The part I am inquiring about is part D in the code. I know I probably dont have it right at all this is just my starting point from looking stuff up online. Any help would be appreciated, thanks.
0 Comments
Accepted Answer
Ameer Hamza
on 2 Oct 2020
Edited: Ameer Hamza
on 2 Oct 2020
It should be something like this
z = sqrt(1/N*sum((Score - mean_student).^2, 2))
5 Comments
Ameer Hamza
on 2 Oct 2020
MATLAB uses following formula for std
The difference is division by N-1 in this case. In your formula, there is a division by N. This is an unbiased estimator of standard deviation. Your formula is a biased estimator. Both are equally valid, and you should use the one given to you. Read the discussion here: https://en.wikipedia.org/wiki/Standard_deviation#Estimation.
You cannot make the MATLAB's std result match your formula.
More Answers (0)
See Also
Categories
Find more on Startup and Shutdown in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!