Standard Deviation result in c and excel is different

[MaggieLow]

I have a problem of translating the standard deviation formula into c programming.
The result come out a bit higher than excel. Do anyone knows how to solve the problem.

float STD_pr_TemSum;
float STD_ps_TemSum;

int count2, m, n, l;

for (m=14; m<NUM_RECORD; m++)
{
count2=1;
n=m;
l=14;
STD_pr_TemSum=0;
STD_ps_TemSum=0;

while(count2<=l)
{
STD_pr_TemSum += pow(PR[n]-MAPR[l],(float)2);
STD_ps_TemSum += pow(PS[n]-MAPS[l],(float)2);
n--;
count2++;
}

STD_pr[m] = sqrt(STD_pr_TemSum/(float)(l-1));
STD_ps[m] = sqrt(STD_ps_TemSum/(float)(l-1));
}

[LB]

Have you tried using double instead of float?

[MaggieLow]

Tried using double instead of float given out the same result, the result difference from excel..

[MaggieLow]

already solve, thank..