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Mathematics

The weights of 150 mangoes were recorded as given below :

Weight in gmsNumber of mangoes
160-17015
170-18024
180-19030
190-20036
200-21024
210-22012
220-2309

Calculate the mean weight (to the nearest gram) by step-deviation method.

Statistics

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Answer

i = Class size = 10.

In table below,

t = xAi\dfrac{x - A}{i}

Class-intervalFrequency (f)Mid-value (x)d = x - Atf × t
160-17015165-30-3-45
170-18024175-20-2-48
180-19030185-10-1-30
190-20036A = 195000
200-2102420510124
210-2201221520224
220-230922530327
TotalΣf = 150Σft = -48

By formula,

Mean = A + ΣftΣf×i\dfrac{Σft}{Σf} \times i

= 195 + 48150×10\dfrac{-48}{150} \times 10

= 195 - 480150\dfrac{480}{150}

= 195 - 3.2

= 191.8 ≈ 192 gms.

Hence, mean = 192 gms.

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