MCQ
Find the incorrect formula from the following:
  • A
    $ \text{mode}=\text{L}+\Big(\frac{\text{f}\text{m}-\text{f}1}{\text{f}\text{m}-\text{f}1-\text{f}2}\Big)\text{h}$
  • B
    $\text{Mean} = \frac{\sum {\text{ fixi }} }{\sum { \text{xi }} }​$
  • C
    $\overline{\text{x}}= \frac{\sum {\text{ fixi }} }{\sum { \text{fi }} }​$
  • D
    $\overline{\text{x}}= \frac{\sum {\text{ fixi }} }{\sum { \text{fi }} }​$

Answer

  1. $\overline{\text{x}}= \frac{\sum {\text{ fixi }} }{\sum { \text{fi }} }​$

Solution:

$\text{ A Median} = \text{L} + \begin{pmatrix} \frac{N}{2} - \text{c.f.} \end{pmatrix} \frac{\text{h}}{\text{f}} , ​ ​ ​ $ 

$ \text{mode}=\text{L}+\Big(\frac{\text{f}\text{m}-\text{f}1}{\text{f}\text{m}-\text{f}1-\text{f}2}\Big)\text{h}$ Where,

L is lower boundary of median class,

N is sum of frequencies, c.f. is cumulative frequency,

h is width of classes, f is frequency of mode class,

$ \text{f}_\text{m}$ is frequency of modal class,

$ \text{f}_\text{1}$ is frequency of pre-modal class,

$ \text{f}_\text{2}$ is frequency of post-modal class Mean is

given $= \frac{\sum {\text{ fixi }} }{\sum { \text{fi }} }​$ Thus, Mean given in option C is incorrect.

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