PROCESSING OF DATA
 The first step in processing of data is classification and tabulation.
 Classification is the process of arranging data on the basis of some common characteristics possessed by them.
 Two approaches in analysing data are:
 Descriptive statistics
 Inferential statistics
 “Descriptive statistics are concerned with describing the characteristics of frequency distributions.” The common methods in descriptive analyses are:
 Measures of central tendency
 Measures of dispersion
 Tabulation, crosstab, contingency table
 Line diagram, bar diagram, pie diagram.
 Histogram, frequency polygon, frequency curve
 Quantile, QQ plot
 Scatterplot
 “The inferential statistics helps to decide whether the outcome of the study is a result of factors planned within design of the study or determined by chance.” Common inferential statistical tests are:
 Ttests
 Chisquire test
 Pearson correlation
Frequency Distribution
 Simple depiction of all the data
 Frequency distribution is a statistical table containing “groups of values according to the number of times a value occurs.”
 The data collected by an investigator is called raw data.
 Raw data is ungrouped data.
 It is not in order.
 Raw data is arranged in order called array.
 The data arranged in ascending order or descending order
Frequency Distribution with Classes
 It is constructed with class intervals.
 It is a frequency distribution of continuous series.
 Raw data arranged as array data.
 Then the data is divided in to groups called classes.
 The first class and the last class are fixed by seeing the lowest and highest values.
 Lowest and highest numbers of each class are called class limits (upper & lower).
 The class limit may be made in two methods:
 Inclusive methods
 Exclusive method
PRESENTATION OF DATA
 Tabular presentation
 Diagrammatic Presentation
 Graphical Presentation
A. Tabular Presentation of Data
 Arranging values in columns is called tabulation.
 E.g. The amount of oxygen content in water samples
Water samples 
Amount of O2 in mL 
1
2
3
4 
4.5
6.9
6.2
5.3 
B. Diagrammatic Presentation of data
 It is a visual form of presentation of statistical data in which data are presented in the form of diagrams such as bars, lines, circles, maps
 Advantages of diagrammatic presentation of data:
 It more attractive
 It simplify complex information
 It saves time
 It helps to make comparison.
 Rules for drawing diagrams
 It should have a title
 Proper scaling should be used.
 Index must be given for better understanding of diagrams
 Common Types
 Line Diagram
 Pie diagram
 Bar diagram
Line diagram
E.g. A traffic survey shows the following vehicles passing a particular bus stop during a hour
Vehicles 
Frequency 
Cars
Lorries
Motor Cycles
Buses 
45
22
6
3 
Total 
76 


Pie Diagram
Example: blood group of 50 students
Group Students
A 5
B 20
AB 10
O 15 

Bar Diagram
Example: yield of various vegetables from a garden.


B. Graphical Presentation of data
 Presenting data in the form of graphs prepared on a graph.
 The graph has two axes: X & Y
 Usually, Independent variable is marked on the Xaxis and dependent variable on the Yaxis.
 Common Types:
 Histogram
 Frequency Polygon
 Frequency curve
Histogram
 Histogram is a graph containing frequencies in the form of vertical rectangles.
 It is an area diagram
 It is the graphical presentation of frequency distribution.
 Xaxis is marked with class intervals
 Yaxis is marked with frequencies
 Histogram differs from bar diagram. The bar diagram is one dimensional, whereas histogram is twodimensional.
 Uses of histogram
 It gives a clear picture of entire data
 It simplifies complex data
 Median and mode can be calculated.
 It facilitates comparison of two or more frequency distributions on the same graph.
Category 
Systolic BP (mmHg) 
Number of Persons7 
1 
100109 
7 
2 
110119 
16 
3 
120129 
19 
4 
130139 
31 
5 
140149 
41 
6 
150159 
23 
7 
160169 
10 
8 
170179 
3 


Frequency Polygon
Frequency Curve
