Download L643: Evaluation of Information Systems

Social Statistics: Chart
Review
Range
 Standard deviation
 Variance
 Using Excel to calculate them

2
Chart
Label everything
 One graph communicate one idea
 Keep things balanced
 Simple is best


3
A picture is worth a thousand words
Frequency distribution


Frequency distribution is a method to represent the
frequency of certain scores.
When you have a data set, such as a testing
scores,

Class intervals
Number of intervals: 5, 10, 20
 Value of interval=range/number of intervals

4
Exercise

50 scores
Set class intervals
 Create a histogram using your hand
 Using Excel to do that

5
Score
47
2
44
41
7
6
35
38
35
36
10
11
14
14
30
30
32
33
34
32
31
31
15
16
17
16
15
19
18
16
25
25
26
26
27
29
29
28
29
27
20
21
21
21
24
24
23
20
21
20
A histogram
Histogram Chart
12
10
8
6
4
2
0
0-4
5-9
14-10
15-19
20-24
25-29
class interval
6
30-34
35-39
40-44
45-49
Excel for Histogram

First, define your bins
The starting point of a bin
 Data analysis Toolpak  histogram

Frequency
Histogram
12
120.00%
10
100.00%
8
80.00%
6
60.00%
4
40.00%
2
20.00%
0
0.00%
24
7
29
19
34
14
39
Bin
9
44
4
49
More
Frequency
Cumulative %
8
Skewness


9
Skewness
Measure of the lack of symmetry of a distribution
 mean>median>mode  positively skewed
 mean<median<mode  negatively skewed
Skewness
10
Skewness
Median for frequency
distributions: N=total
number of respondent
(n=1414), If n=even
number, n/2=707, if n=
odd, (n+1)/2. So in fy
column, 707 fits to 717
which has 3 siblings, so
median=3. Or in c%,
50% fits to 63.2%,
which is 3 siblings
11
Skewness
12
Kurtosis

13
Kurtosis: the degree of peakedness or flatness of a
probability distribution
Variability

14
Variability (S-p97-Fig 4.14)
Frequency distribution

Excel: SKEW() and KURT()


15
Skewness characterizes the degree of asymmetry of a
distribution around its mean. Positive skewness indicates a
distribution with an asymmetric tail extending toward
more positive values. Negative skewness indicates a
distribution with an asymmetric tail extending toward
more negative values.
Kurtosis characterizes the relative peakedness or flatness
of a distribution compared with the normal distribution.
Positive kurtosis indicates a relatively peaked distribution.
Negative kurtosis indicates a relatively flat distribution.
Exercise

16
From General Social Survey
2010, we reported the number
of children showed in the
subsample of male and female
respondents.
 Create a histogram using
your hand
 Using Excel to do that
 Mean, mode and median
 Skewness (for more details
on how to calcualte
skewness,
http://www.tc3.edu/instruct
/sbrown/stat/shape.htm)
# of Children Males
Females
0
94
92
1
52
72
2
71
127
3
47
91
4
30
38
5 or more
33
27
Total(N)
327
447