Chapter 13 · Question 2

Explain the assumed mean method for grouped data.

Answer Revealed

Direct Answer:

Choose an assumed mean

a

, compute

d_i=x_i-a

, then use

\bar{x}=a+\frac{\sum f_i d_i}{\sum f_i}

Assumed mean reduces calculations by measuring deviations from a convenient central value.

In the assumed mean method, choose a class mark near the centre as

a

. For every class, calculate

d_i=x_i-a

. Then calculate

f_i d_i

and use

\bar{x}=a+\frac{\sum f_i d_i}{\sum f_i}

. This is algebraically the same as the direct method but often easier.

Choose an assumed mean $a$ , compute $d_i=x_i-a$ , then use $\bar{x}=a+\frac{\sum f_i d_i}{\sum f_i}$ .
Use the NCERT formula or theorem carefully.
Write units and final conclusion where applicable.

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