Stat 2 data presentation2
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Transcript of Stat 2 data presentation2
Data presentation
Prepared byAssis. Prof.
Namir G. Al-Tawil
The ordered array
It is the first step in the process of data organization.
An ordered array is a listing of values of a collection in order of magnitude from the smallest value to the largest value.
It enables one to determine quickly the value of the smallest measurement, and the value of the largest measurement, and enable one to determine roughly the proportion of people lying below or above certain value.
The frequency distribution
One of the ways of data summarization. To group a set of observations, we
select a set of class intervals. There must be no overlapping between these intervals.
Too few intervals are undesirable because of the resulting loss of information. If too many intervals are used, the objective of summarization can not be met. The appropriate No. of class intervals is 6-15.
The frequency distribution, cont.
Sturge’s rule (formula): K = 1 + 3.322 (log10 n) K = No. of class intervals. n = sample size. Note that this rule is not final, you can
increase or decrease the No. of class intervals for convenience and clear presentation.
The frequency distribution, cont.
The width (W) of class interval, in general, is equal, but sometimes this is not possible.
W = R/K R = Range (difference between smallest
and largest observation). For convenience, a width of 5 units or 10
units is used.
Example of a frequency distribution table of 169 subjects of different ages
Class interval
Frequency Cumulative frequency
Relative frequency
Cumulative R. Frequency
10-19 4 4 0.0237 0.0237
20-29 66 70 0.3905 0.4142
30-39 47 117 0.2781 0.6923
40-49 36 153 0.2130 0.9053
50-59 12 165 0.0710 0.9763
60-69 4 169 0.0237 1.0000
Total 169 1.0000
Figure 1. Success rate by college
0
10
20
30
40
50
60
70
80
90
Erbil Sulaimany DuhokCollege
Succ
ess
rate
%
Age (years)
0
1
2
3
4
5
6
17.5 20 22.5 25 27.5 30 32.5 35 37.5 40 42.5 45 47.5
freq
uenc
y
The Frequency Polygon
Distribution of Sample by Age
Line Graph
0
10
20
30
40
50
60
70
10 to 19 20 to 29 30 to 39 40 to 49 50 to 59 60 to 69
Age (years)
fre
que
ncy
Figure 1. Distribution of sample by sex
Males, 150, 33%
Females, 300, 67%