Calculating Mean using Step Deviation Method
Calculating Mean using Step Deviation Method
Calculating Mean Using Step Deviation Method:
Sometimes, while calculating mean using assumed mean method we find that the deviation d, are divisible by a common number . Let us assume the common factor as h. The deviation is then divided by h and the resultant number is denoted by u. In this way the value of d is reduced to a great extent and hence the calculations become more simple. The method is called the step-deviation method, and we can express it
Where , a = Assumed mean , ,
h=class size
Illustration: The table below gives the percentage distribution of female teachers in the primary schools of rural areas of various states and union territories (U.T.) of India. Find the mean percentage of female teachers by step deviation method.
| Percentage of female teacher | 15-25 | 25-35 | 35-45 | 45-55 | 55-65 | 65-75 | 75-85 |
| number of status/U.T | 6 | 11 | 7 | 4 | 4 | 2 | 1 |
Solution : Let us find the class mark, xi, of each class, and put them in a column
Here we take a = 50,
h = 10,
| Percentage of female teachers | Numbers of states or U.T. |
Class Mark |
|||
|
15-25 25-35 35-45 45-55 55-65 65-75 75-85 |
6 11 7 4 4 2 1 |
20 30 40 50 60 70 80 |
-30 -20 -10 0 10 20 30 |
-3 -2 -1 0 1 2 3 |
-18 -22 -7 0 4 4 3 |
| Total | 35 | -36 |
Using the step-deviation method,
Therefore, the mean percentage of female in the primary schools of rural areas is 39.71.
What will be the value of
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| Right Option : D | |||||||||||||||
| View Explanation | |||||||||||||||
What will be the value of mean by using step - deviation method for the following distribution :
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| Right Option : B | |||||||||||||||
| View Explanation | |||||||||||||||
In the formula, | |||
| Right Option : C | |||
| View Explanation | |||
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