This document discusses descriptive and inferential statistics, and how to organize data into frequency distribution tables. Descriptive statistics summarize data, while inferential statistics are used to generalize results to populations. Frequency distribution tables arrange data into class intervals to show the distribution of a variable or combination of variables. The tables include the class, frequency, relative frequency, and cumulative frequency. An example frequency distribution table is provided using data on number of children from 20 individuals.
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In Medicine and related paramedical practices we will be dealing with qualitative variables, that
could be nominal or ordinal, and with quantitative variables, that could be continuous or discrete.
The classification of the data, according to the scale of measurement used, is very important.
The classification of data is usually made by frequency distribution tables of one variable or a
combination of variables.
The scale of measurement is the way in which each element may be represented by a given
measure unit. Any scale of measurement must have two main conditions:
- To be exhaustive: Include all elements
- To have classes or categories mutually exclusive Each element ought to be
considered only once
For data to be more easily appreciated, it is often useful to arrange the data in the form of a table.
Quite often, the presentation of data in a meaningful way is done by preparing a frequency
distribution table.
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- : is the characteristic by which the data of a variable are grouped.
- : could be defined as the way in which the characteristics of the
quantitative data are used with grouping purposes.
- : is the difference between the lower and
upper class boundaries and is called "class width", class length" or " class size".
Class width= Maximum value of data - minimum value of data
number of class intervals wanted
- is midpoint of a class interval
- : frequency or class frequency is the number of observations
falling into each class or class interval.
- : is the absolute frequency of class divided by the total
frequency of all classes.
The relative freq. of a class= absolute frequency of the class divided by
Total frequency of all classes.
- is the sum of the frequencies up to a given class or class interval.
- When the class interval has lower and upper class limits.
- when at least theoretically either no upper class limit or no lower
class
limit indicated.
The table below shows the data collected from 20 individuals.
7 M 3 176.4
6 M 4 180
5 F 3 167.2
4 M 0 168.3
3 F 0 149
2 M 1 164.2
1 M 2 151.3
Number of
element Sex
Number of
children
Height
(Cms.)
15. 15
20 F 5 168
19 M 6 172.4
18 M 4 167.3
17 F 3 159.3
16 M 2 155
15 M 1 157
14 F 0 152
13 F 1 148.2
12 F 2 145
11 M 3 160
10 M 4 157.2
9 F 5 145.1
8 M 6 151
We want to do a frequency distribution tables for the data of the 3 variables listed in the table.
