Question

statistics mean formulas for 1st puc
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Answer 1

Mean

To find the mean of grouped data,it is assumed that the frequency of each class interval is centred around the midpoint.

(i) The direct method

$\green{X=\frac{∑fixi}{∑fi }}$

where

• xi(class marks) is the midpoint of the ith class interval
• f_i is the corresponding frequency.

(ii) The assumed mean method

$\red{X¯=a+ \frac{∑fidi}{∑fi}}$

•  a = assumed mean
• d_i=x_i-a are the deviations of x_i from a for each i

(iii) The step deviation method

$\orange{X=a+ \frac{∑fiui}{∑fi} ×h}$

where

• a is assumed mean
• h is the class size
• $u_1= \frac{ x_i-a}{h}$

$\: \: \: \: \: \: \: \: \: \: \huge \bold{@WildCat7083 }$