Population Standard Deviation :

// SD of a population
#include <math.h>
#include <stdio.h>
float calculateSD(float data[]);
int main() {
    int i;
    float data[10];
    printf("Enter 10 elements: ");
    for (i = 0; i < 10; ++i)
        scanf("%f", &data[i]);
    printf("\nStandard Deviation = %.6f", calculateSD(data));
    return 0;
}

float calculateSD(float data[]) {
    float sum = 0.0, mean, SD = 0.0;
    int i;
    for (i = 0; i < 10; ++i) {
        sum += data[i];
    }
    mean = sum / 10;
    for (i = 0; i < 10; ++i) {
        SD += pow(data[i] - mean, 2);
    }
    return sqrt(SD / 10);
}

Enter 10 elements: 2
5
7
6
12
19
24
35
47
52
Standard Deviation = 17.218885