Class 10 · Mathematics (Basic) · Unit 13: Statistics

Mean of Grouped Data

Lesson 1 of 5

For a frequency distribution with classes and midpoints

x_i

and frequencies

f_i

, direct method:

\bar x = \dfrac{\sum f_i x_i}{\sum f_i}

. Assumed-mean method: pick

a

near the middle;

d_i = x_i - a

; then

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

. Step-deviation: with

u_i = (x_i - a)/h

\bar x = a + h\cdot\dfrac{\sum f_i u_i}{\sum f_i}

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