MEV 019: Unit 05 - Data Management
5.1 Introduction
Data management is the systematic organization,
processing, and presentation of collected data to facilitate analysis,
interpretation, and decision-making. In environmental science, the effective
management of data ensures that complex ecological information is structured in
ways that reveal patterns, trends, and relationships essential for informed
conclusions.
5.2 Objectives
After studying this unit, you will be able to:
- Understand various types of frequency distributions.
- Learn how to tabulate and classify data effectively.
- Recognize the importance of diagrammatic and graphical
representation.
- Create and interpret bar diagrams, pie charts, pictograms,
cartograms, and frequency graphs.
5.3 Frequency Distribution
A frequency distribution is a tabular or
graphical display showing the frequency (number of times) of various outcomes
in a dataset.
5.3.1 Discrete Frequency
Distribution
Used for discrete variables (countable
items such as number of species, number of factories). It lists each distinct
value along with its frequency.
Example:
|
Number of Factories |
Frequency |
|
1 |
3 |
|
2 |
5 |
|
3 |
7 |
5.3.2 Continuous Frequency
Distribution
Used for continuous variables (e.g.,
temperature, rainfall) grouped into class intervals.
Example:
|
Rainfall (mm) |
Frequency |
|
0–10 |
2 |
|
11–20 |
6 |
|
21–30 |
9 |
5.3.3 Relative Frequency
Distribution
Shows the proportion of total data points
within each class or category, often expressed as percentages.
5.3.4 Cumulative Frequency
Distribution
Shows the running total of frequencies. It is
useful for identifying medians and percentiles.
5.4 Tabulation of Data
Tabulation refers to arranging data in
rows and columns for easy comparison and understanding.
5.4.1 Objectives of Tabulation
- Simplify complex data.
- Facilitate comparison.
- Enable quick reference.
- Help identify trends.
5.4.2 Components of a Table
- Title
- Table Number
- Headings (columns and rows)
- Body (data entries)
- Footnotes (if needed)
- Source (for secondary data)
5.4.3 Types of Tables
- Simple Table: One characteristic.
- Complex Table: More than one characteristic (e.g., location and time).
- Frequency Table: Shows distribution of values.
5.5 Diagrammatic
Representation of Data
This involves the use of diagrams and visuals
to present statistical data.
5.5.1 Significance
- Makes data visually appealing and easier to understand.
- Useful for presentations and public communication.
5.5.2 Different Types of
Diagrams
- Bar diagrams
- Pie charts
- Pictograms
- Cartograms
5.5.3 Components of Diagrams
- Title
- Scale or proportion
- Axis labels (where applicable)
- Legend (if colors/symbols used)
5.6 Bar Diagrams
5.6.1 Simple Bar Diagrams
Represent a single variable across categories
using uniform-width bars of different lengths.
5.6.2 Multiple Bar Diagrams
Used to compare two or more related variables
side-by-side for each category.
5.6.3 Sub-Divided Bar Diagrams
A single bar is divided into segments showing
component parts of a whole (also called stacked bar charts).
5.7 Pie Diagram or Pie Chart
A pie chart represents parts of a whole
as sectors of a circle. Each sector's angle is proportional to the frequency it
represents.
Formula for angle = (Value / Total) × 360°
Used for showing percentage distribution, like
the proportion of land use types or energy sources.
5.8 Pictograms or Pictorial
Diagrams
Use images or icons to represent data (e.g.,
one tree symbol represents 1,000 trees). These are visually appealing and often
used in public awareness material.
5.9 Statistical Maps or
Cartograms
Maps that represent statistical data
geographically. Examples include:
- Choropleth maps: Areas shaded according to pollution levels.
- Dot maps: Show spatial distribution of events like disease outbreaks.
- Isoline maps: Indicate elevation or pollution concentration.
5.10 Graphical Presentation of
Statistical Data
5.10.1 Methods of Graphical
Presentation
- Histogram
- Frequency Polygon
- Frequency Curve
- Ogives (Cumulative frequency curves)
5.10.2 Histogram
A bar graph for continuous data. Bars are
adjacent to show the continuous nature of data (e.g., temperature
distribution).
5.10.3 Frequency Polygon
A line graph that joins midpoints of each class
interval. Helps compare multiple distributions on the same graph.
5.10.4 Frequency Curve
A smoothed version of the frequency polygon;
often used in probability distributions.
5.10.5 Cumulative Frequency
Curves (Ogives)
There are two types:
- Less than Ogive: Shows cumulative frequency from lowest value upward.
- More than Ogive: Cumulative frequency from the highest downward.
Used for identifying median, quartiles, and
percentiles.
5.11 Let Us Sum Up
In this unit, we learned about organizing,
classifying, and visually presenting environmental data using frequency
distributions, tables, diagrams, and graphs. Proper data management ensures
that environmental researchers can identify patterns and make evidence-based
decisions.
5.12 Key Words
- Frequency Distribution: Summary of how often
different values occur.
- Tabulation: Systematic arrangement of data in rows and columns.
- Histogram: Graphical representation of frequency data for continuous
variables.
- Bar Diagram: Visual tool using rectangular bars to compare values.
- Pie Chart: Circular chart representing parts of a whole.
- Ogive: Cumulative frequency curve.
- Cartogram: Map with statistical data overlay.
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