Statistical Graphs
The graphical techniques are very considerable aid of summarizing and analyzing data or even the results of a study . Let x be the variable and f it's frequency ,then the followings are some of the graph types :- ׀ : For Discrete Variables: When x is a discrete variable then the following types may be applied ,(1)(2)
II : For Continuous Variables:
When the frequency table contains continuous classes then the midpoints do present the X values (N.B. the count represent the frequency) .))
The Polygon
(5)Notes:
1. More than one set of data can be used . 2. Using the mid upper base of the histogram then join them to have the polygon or curve . 3. Both the polygon and the curve use mid points with the frequency to present the points for the graph . 4. A comparison of two or more variables can be done on the same graph . 5. Don't contain so much lines and symbols more than the eye can follow . 6. Don't forget the title of the graph . 7. Scale and units should be represented on graph axis . 8. The symbol ( ⁄⁄ ) means cutting a part from the beginning of the axis .(7)Scatter Diagram For the scatter diagram the data must be given as pairs X and Y ,and each of size n .
(8)
General suggestions for design used for data : 1. Choose the method more effective for data and purpose . 2. Multi (bars or columns) are suitable for comparing discrete variables . 3. Polygon and curve are suitable for comparing continuous variables . 4. Scatter diagrams are good for showing relationships .
(9)
H.W(1) The following table shows no. of patients visited 5 different clinical centers at a certain week Represent the followings using statistical graphs: 1. Total no. of patients in the five different centers , (use pie chart). 2. No. of patients( ♀& ♂ ) of the five centers in the same chart , (use multi columns). 3. No. of patients(male & female) of the five centers in the same chart , (use percent columns ) . 4. No. of females of the five centers , (use bar chart) . (10) clinical centers
Males
Females
Total
1
15
10
25
2
30
30
60
3
20
25
45
4
10
15
25
5
20
20
40
Total
95
100
195
H.W(2) The table below gives the weight of 100 men & 90 women . Show the followings in charts :- 1. Men’s weight in histogram . 2. Women’s weight in polygon . 3. Men’s & women’s weights in curves (on the same chart) . Weight Classes
60-
65-
70-
75-
80-
85-
90-
95-100
Total
Men
9
11
14
20
19
15
8
4
100
Women
12
20
13
19
15
8
2
1
90
H.W(3) The following is the skinfold thickness (mm) measured for 57 male subjects .Find the polygon from the histogram H.W(4) The followings are the age & the 6 hours postoperative PaO2 in 10 patients receiving 50% nitrous oxide with oxygen during the operation Patient’s no. 1 2 3 4 5 6 7 8 9 10 Age (years) 45 24 34 36 22 47 39 37 44 53 PaO2 (mm.Hg) 76 94 78 99 91 74 95 82 86 87 Estimate the relationship between age & PaO2 by eye . Skinfold thickness
0.0-
5.0-
10.0-
15.0-
20.0-
25.0 – 30.0 No. of males
2
9
20
15
8
3