calculate average marks of the following students using. a) Direct method b) step deviation method . marks (x) 0-10 10-20 20-30 30-40 no-50 50-60 60-70. Number of students (F) 5 , 12, 15, 25, 8, 3, 2.
Answers
Hey mate ! This is your answer
Concept
A number expressing the central value in a set of data, which is calculated by dividing the sum of the values in the set by their number is called average.
Given
Class intervals Number of students
0-10 5
10-20 12
20-30 15
30-40 25
40-50 8
50-60 3
60-70 2
To find
Calculate the average marks by direct method and step deviation.
Explanation
We know that average is mean and mean by direct method is equal to ∑fX/∑f where X is mid point and f is frequency.
Mean by direct method=2110/70
=30.14
Mean by step deviation method can be calculated as under:
Mean = A+ ∑f d/∑f where A is assumed mean and d is deviation of mid point from assumed mean, f is frequency. Let the assumed mean be 35.
Mean by step deviation method=35-340/70
=(2450-340)/70
=2110/70
=30.14
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