Page 30 - Basic Statistics

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2. Second quartile (Q2) is the observation value that lies in the location of (2

(n +1) / 4)th in the ordered data. Partitioning the data on 50% down and
50% up. Second quartile of a data set is the same as the median of the

data.

3. Third quartile (Q3) is the observation value that lies in the location of the

(3 (n +1) / 4)th in the ordered data. Partitioning the data on 75% down

and 25% up.

c. Variance

For the set of data on population X1, X2 , …, XN , variance of population

can be calculated with the following formula.

N
 ( X − X ) 2
i
2
Variance :  = i= 1
N

For the set of data on sample X1, X2 , …, Xn , variance of sample can be

calculated with the following formula.

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

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