By | 05.03.2017

# Write a C Program for Mean,Variance & Standard deviation of n numbers

Here in this c program,  we need to find out mean variance and standard deviation of n numbers, for that we need to know what is meant by mean, standard deviation and variance.

Mean : it is the average of a number of elements in a set of values. which means just add the values in a set and divide the sum with the number of elements in the set.

Variance : It is the average of squared difference of mean and the values of the data set it is  called the spread of data within a sample of data.

Standard deviation : after we got the variance we get the standard deviation by taking square root of the variance

In this c program we are taking the values for a set from the users, the mean is calculated by taking average of the sum by using a for loop . after that we need to calculate variance using the formula “value=a[i]-mean; sumsqr=sumsqr + value*value;” and var = sumsqr/ n; then now we need to calculate the standard deviation of the set, we use SD = sqrt(var) formula in this c program.

Here is source code of the C program to calculate the mean, variance & standard deviation. The C program is successfully compiled and run(on Codeblocks) on a Windows system. The program output is also shown in below.

## SOURCE CODE : :

```#include<stdio.h>
#include<math.h>
int main()
{
int i,n;
float std_dev,sum=0,sumsqr=0,mean,value,variance=0.0,a;
printf("Enter value of n : ");
scanf("%d",&n);
printf("\nEnter numbers : ");
for(i=0;i<n;i++)
{
printf("\nNumber %d : ",i+1);
scanf("%f",&a[i]);
sum=sum+a[i];
}
mean=sum/n;
sumsqr=0;
for(i=0;i<n;i++)
{
value=a[i]-mean;
sumsqr=sumsqr+value*value;
}
variance=sumsqr/n;
std_dev=sqrt(variance);
printf("\nMean of %d numbers = %f\n",n,mean);
printf("\nVariance of %d numbers = %f\n",n,variance);
printf("\nStandard deviation of %d numbers = %f\n",n,std_dev);
return 0;
}```

## OUTPUT : :

```Enter value of n : 7

Enter numbers :
Number 1 : 23

Number 2 : 45

Number 3 : 12

Number 4 : 66

Number 5 : 58

Number 6 : 31

Number 7 : 67

Mean of 7 numbers = 43.142857

Variance of 7 numbers = 405.551025

Standard deviation of 7 numbers = 20.138298```
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