Biostatistics Study Materials

Statistical Data /Variables – Types and Classification (Biostatistics Short Notes)

What is Data or Variable

Statistical Data / Variables – Introduction
(Classification of Statistical Data / Variable – Numeric vs Categorical)

What is ‘data’ or ‘variable’?

Ø  Data is a set of values of qualitative or quantitative variables.

Ø  In biostatistics (also in statistics) data are the individual observations.

Ø  The scientific investigations involve observations on variables.

Ø  The observations made on these variables are obtained in the form of ‘data’.

Ø  Variable is a quantity or characteristic which can ‘vary from one individual to another’.

Ø  Example: Consider the characteristic ‘weight’ of individuals and let it be denoted by the letter ‘N’. The value of ‘N’ varies from one individual to another and thus, ‘N’ is a variable.

Ø  Data and variable are not exact but used frequently as synonyms.

Ø  The variables can also be called as ‘data items’.

Ø  Majority of the statistical analysis are done on variables.

Type of Variables in Statistics

Statistical variables can be classified based on two criterion (I) Nature of Variables and (II) Source of variables

I. Classification of variable based on Nature of Variables

Ø  Based on the nature of variables, statistical variables can be classified to TWO major categories such as (1) Numerical and (2) Categorical.

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Biostatistics Study Materials

Biostatistics Introduction (Significance, Applications and Limitations of Statistics)

Applications and Limitations Biostatistics

Biostatistics – Introduction
(Significance, Applications and Limitations of Biostatistics)

What is Statistics?

Statistics is a branch of applied mathematics which deals with the collection, classification, analysis and interpretation of data. The word statistics is derived from the Latin word ‘status’ means a ‘political state’ or ‘government’.

What is Biostatistics?

Biostatistics is a branch of biological science which deals with the study and methods of collection, presentation, analysis and interpretation of data of biological research. Biostatistics is also called as biometrics since it involves many measurements and calculations. In biostatistics, the statistical methods are applied to solve biological problems. Basic understanding of biostatistics is necessary for the study of biology particularly doing research in biological science. The statistics will help the biologist to: (1) understand the nature of variability and (2) helps in deriving general laws from small samples.

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Biostatistics Study Materials

Graphical Representation of Data (Frequency Polygon, Frequency Curve, Ogive and Pie Diagram)

Graphs for Data Representation

Graphical Representation of Data: Part 2
(Data Representation Methods: Frequency Polygon, Frequency Curve, Ogive and Pie Chart)

This post is the continuation of the Previous Post (Graphical Representation of Data Part 1).

(3). Frequency Polygon

Ø  The Frequency Polygon is a curve representing a frequency distribution.

Ø  In frequency polygon, the mid values of each class are first obtained.

Ø  In a graph paper, the frequency of each class is plotted against the mid-value of class (on the X axis).

Ø  Then these points are then joined by a straight line.

Ø  This straight line is extended in both directions to meet on the X axis.

Ø  The first point is joined to the lower limit of the first class and the last point is joined to the upper limit of last class. Thus, the frequency polygon is a closed graph.

Ø  The graph now obtained is called Frequency polygon.

Example: Construct a Frequency Polygon using the following data


data for frequency polygon

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Biostatistics Study Materials

Graphical Representation of Data (Line Graph, Bar Diagram & Histogram)

Data Representation

Graphical Representation of Data: Part 1
(Diagrammatic Data Representation: Line Chart, Bar Diagrams and Histogram)

Graphical Representation of Data / Variables

Ø  The data presentation in statistics may be Numerical or Graphical.

Ø  If the data is presented in the numerical form, it will not attract the attention of the audience.

Ø  In order to attract the attention of the audience, Graphical Representation method is usually adopted.

Ø  Graphical Representation: It is the representation or presentation of data as Diagrams and Graphs.

Ø  The statistical graphs were first invented by William Playfair in 1786.

Ø  In graphical data representation, the Frequency Distribution Table is represented in a Graph.

Advantages of Graphical Representation of Data

Ø  Data are presented pictorially.

Ø  Give better insight and understanding of the data.

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Biostatistics Study Materials

Frequency Distribution Table: Definition with Examples + PPT

What is Frequency Distribution?

Frequency Table / Frequency Distribution
(Definition, Construction and Significance of Frequency Distribution)

In the previous post, we have discussed the concept of Tables and Tabulation of Variables in Statistics. Here we will discuss the concept of Statistical Tables better known as Frequency Distributions of Frequency Tables.

Statistical Tables

Ø  There are different types of tables in statistics.

Ø  The most common type of table in the statistics is ‘Frequency Table’ or ‘Frequency Distribution’.

Ø  Frequency Distribution definition: “The frequencies of occurrence of data values are presented in tabular form in the ascending order of magnitude”.

Ø  It is a statistical table that shows the frequency of various outcomes in a sample.

Ø  The frequency table shows the total for each category or group of data.

Example: A raw data and its frequency distribution is given below

Example of Frequency table

Ø  A frequency table composed of TWO components:

(1).   Class

(2).   Frequency

Class and Frequency

Ø  When a population is divided into small groups on the basis of some attributes or characteristics, each such group is considered as a class.

Ø  In each class, the number of individual value of that particular feature is one or many.

Ø  Such occurrence of individuals in a class is called frequency.

Thus a Frequency Table is “the arrangement of distribution of individuals of a class which displays the frequency of the individuals according to a characteristic.”

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