Calculate the standard deviation using step deviation method.
class Frequency
0-10 2
10-20 4
20-30 6
30-40 8
40-50 6
50-60 4
60-70 2
Answer is 15.81
but it is applying only for first three methods but it is 1.581 in standard deviation method

please clarify

Meghana, we use the following formula to calculate standard deviation using step deviation method.

Standard deviation = fdxIN- fdxIN2 × h
Where refers to the class size which is 10 in the given question.I thing you forgot to treat h while solving the question yourself. So you just have to multiply your current answer by 10.

If this is not the case and your answer is different for some other reason using step deviation method, do get back to us. 


  • 3
my answer 15.81 is coming by step deviation
  • -1
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