Question

mean deviation for mean the following distribution:
Marks :
20-30 30-40 40-50 50-60 60-70 70-80 80-90
No.of students = 3, 6 ,13, 15, 14 ,5 ,4
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Answer 1

Answer:

To calculate the standard deviation of those numbers:

Work out the Mean (the simple average of the numbers)

Then for each number: subtract the Mean and square the result.

Then work out the mean of those squared differences.

Take the square root of that and we are done!