Page 27 - Basic Statistics

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2.1.2 MEASURES OF CENTRAL LOCATION FOR GROUPED DATA
Grouped data is data that is summarized according to classes. First, the

data set is partitioned into subsets, called class. Wide class called class intervals.

Generally, the width of the class is created equal, although for the benefit or

condition of the data, the class may not be the same width. Determination of the

width of the class is done by first conducting a review of the range of the data,
ie the width between the maximum value with the minimum value. A group of

observations in a particular class is calculated amount, and expressed as the

frequency of the class.

Example of the grouped data :

Table 2.1 Grouped data

Frequencies Midpoint Cumulative
Classes ( fi ) ( xi ) fi. xi Frequencies
( Fi )

0 - < 5 2 2,5 5 2

5 - < 15 6 10 60 8
15 - < 25 20 20 400 28

25 - < 35 15 30 450 43
35 - < 45 8 40 320 51

45 - < 100 4 72,5 290 55

Total n = 55 1.525

The formula for determining measures of central location are :
p
 f i x . i

Mean : X = i= 1
n

f c
Median : Md = L + . W
f m

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