Here in this C program, we need to find out **Mean, Variance,** and **Standard deviation**; we need to know what is meant by Mean, Standard deviation, and Variance.

**Mean**: it is the average of all elements in a set of values. Means add the values in a set and divide the **sum** with the number of elements. For example if a set has 3 numbers** **[1,2,3] then the mean is calculated using **1+2+3 = 6/3 =2**.

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

**Standard deviation**: after we found the **variance**, we can calculate the standard deviation by taking the square root of the variance.

In this c program, we take the values and save that in an array. The mean calculation is by taking the average of the sum by using a '`for loop`

' after that, we need to calculate variance using the formula.

```
"sum1 = sum1 + pow((x[i] - avrg),2)"
var = sum1 / (float) n;
```

After calculating the variance, it is easy to find the standard deviation. Estimate the standard deviation of the set; we use the **sd = sqrt(var)** formula in this c program. Finally, we have to display the mean, variance, and standard deviation using `printf`

in the c language.

**STEP 1**: Include the Header files into the C program to use the built-in functions.

**STEP 2**: Define and initialize the Array and the variables used in the program.

**STEP 3**: Accept the value for the number of terms from the user using `printf`

and `scanf`

functions.

**STEP 4**: Accept the numbers from the user and add those numbers into an Array using '**for loop**' and `scanf`

.

**STEP 5**: Open a '`for loop`

' from **zero** to the number of terms to calculate the **Mean**.

**STEP 6**: Calculate **Mean** by finding the **Sum** and divide that with the number of terms.

**STEP 7**: Open another For loop from zero to '**n**' to find the **Variance**.

**STEP 8**: Calculate the **Variance** using the formula **sum1 = sum1 + pow((x[i] - avrg),2** and apply the **sum1** in main formula **var = sum1 / (float) n**.

**STEP 9**: Calculate the Standard deviation by taking the square root of **Variance**.

**STEP 10**: print the **Mean**, **Standard deviation**, and **Variance **using `printf`

built-in functions in C.

` ````
#include <stdio.h>
#include <math.h>
#define MAXSIZE 10
void main()
{
float x[MAXSIZE];
int i, n;
float avrg, var, SD, sum=0, sum1=0; /* declares the variables avrg, Sd, sum as float */
printf("Enter the value of N\n"); /* accepts values from user */
scanf("%d", &n);
printf("Enter %d real numbers\n",n);
for (i = 0; i < n; i++)
{
scanf("%f", &x[i]);
}
for(i=0; i<n; i++) /* Compute the sum of all elements */
{
sum = sum + x[i]; /* calculating the mean using the equation */
}
avrg = sum /(float) n;
for(i=0; i<n; i++) /* Compute variance and standard deviation */
{
sum1 = sum1 + pow((x[i] - avrg), 2); /* calculate the variance using general equation */
}
var = sum1 / (float) n;
SD = sqrt(var); /* calculating standard deviation */
printf("Average of all elements = %.2f\n", avrg);
printf("Varience of all elements = %.2f\n", var);
printf("Standard deviation SD = %.2f\n", SD); /* prints the output mean, standard deviation, and variance */
}
```

Enter the value of N 6 Enter 6 real numbers 12 34 10 50 42 33 Average of all elements = 30.17 Varience of all elements = 215.47 Standard deviation SD = 14.68