Page 33 - Basic Statistics

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 n  2
  X 
n  i 
 X 2 −  i= 1 n 
i
2
Variance S = i= 1
n 1 -

7484 − (( 230 ) 2 / 10 )
=
10 − 1

= 243.78

d. Standard deviation :

The standard deviation is the square root of the variance. If you have

obtained variance S = 243.78 then the standard deviation is
2
S = 243 . 78 = 15.61

2.2.2 DISPERSION OF GROUPED DATA

In grouped data, how to calculate the first quartile (Q1) and third

quartile (Q3) equal to how to calculate the median.

n i F −

Qi = L i q + 4 1 - i . W
i q
f
i q

Where,

Qi = (i)th quartile ( i = 1, 2 , 3 )

Lqi = lower limit of the (i)th quartile class interval

Fi-1 = cumulative frequency for a class below of the (i)th quartile class

interval
fqi = frequency of the (i)th quartile class interval

Wqi = width of the (i)th quartile class interval

~~* CHAPTER 2 NUMERICAL MEASURES TO SUMMARIZE DATA *~~