# Learn How to Calculate Reliability Coefficient - Tutorial

## Learn How to Calculate Reliability Coefficient - Tutorial

##### Definition:

Reliability coefficient is used to compute the association of two set of values.

#### Formula:

Reliability Coefficient = (N / (N-1)) ( (Total Variance - sum of Individual Variance) / Total Variance)
###### Where,

N - is number of Tasks

##### Example:

A project was undergone with three Persons (P) and they are allocated with three different Tasks (T). Find the Reliability Coefficient? P0- T0 = 10 P1- T0 = 20 P0- T1 = 30 P1- T1 = 40 P0- T2 = 50 P1- T2 = 60

#### Solution:

##### Given,

Number of Students (P) = 3 Number of Tasks (N) = 3

##### To Find,

Reliability Coefficient,

###### Step 1:

Let us first calculate the average score of the persons and their tasks, The average score of Task (T0) = 10 + 20 /2 = 15 The average score of Task (T1) = 30 + 40 /2 = 35 The average score of Task (T2) = 50 + 60 /2 = 55

###### Step 2:

Next, calculate the variance for Variance of P0- T0 and P1- T0: Variance = square(10-15) + square(20-15) / 2 = 25 Variance of P0- T1 and P1- T1: Variance = square(30-35) + square(40-35) / 2 = 25 Variance of P0- T2 and P1- T2: Variance = square(50-55) + square(50-55) / 2 = 25

###### Step 3:

Now, calculate the individual variance of P0- T0 and P1- T0, P0- T1 and P1- T1, P0-T2 and P1-T2. To calculate the individual variance value, we should add all the above calculated variance values. i.e. Sum of Individual Variance = 25+25+25=75

###### Step 4:

Calculate the Total variance. Variance= square ((P0- T0) - average score of Person 0) = square (10-15) = 25 Variance= square ((P1- T0) - average score of Person 0) = square (20-15) = 25 Variance= square ((P0- T1) - average score of Person1) = square (30-35) = 25 Variance= square ((P1- T1) - average score of Person1) = square (40-35) = 25 Variance= square ((P0- T2) - average score of Person2) = square (50-55) = 25 Variance= square ((P1- T2) - average score of Person2) = square (60-55) = 25 Now, add all the values and calculate the total variance, Total Variance= 25+25+25+25+25+25 = 150

###### Step 5:

Finally, substitute the values in the below given formula to find Reliability Coefficient RC = (N/(N-1)) * ( (Total Variance - Sum of Variance) / Total Variance) = 3/ (3-1) * (150-75)/150 = 0.75