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# Finding the Standard deviation from a structure of numbers

Posted on 2003-11-25

Im trying to find the standard deviation from a structure of numbers.

the array is in the format:

s[x].sid= 301111;

s[x].mark= 50;

s[x].grade= 'A';

were x is incremented for every user.

heres the code for the standard deviation, its in the form of a function initalised using:

float stdDev(struct student s[], int n);

and called using:

stdDev(staff,ARR_SIZE);

heres the function... it just crashes! theres 5 entrys, which should be passed to the function in n

float stdDev(struct student s[], int n)

{

int x;

float mean, sigma;

mean = s[x].sid / n;

for (x=0; x<5; x++) n += (mean - s[x].mark)*(mean-s[x].mark);

sigma = sqrt(n/5);

printf("Std Deviation is %f",sigma);

return sigma;