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Measuring Variables
Biological variables can be grouped as:
- Quantitative,
- Ranked
- Qualitative.
Quantitative variables
These can be described by means of a number. There are two basic types:
- Continuous variables
Length and height are examples usually measured against a measurable scale.
Example: Height of plants in different fertilisers.
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Discontinuous (discrete) variables
These are usually measured by counting the number in a category.
Examples: Number of eggs in a nest.
Ranked variables
These provide data which can be listed in order of magnitude (i.e. ranked)
Example 1
Health disease categories in Pyrethrum survey
Example 2
A familiar example is the abundance of an organism in a sample, which is often expressed as a series of ranks, eg
| 1 |
Rare |
| 2 |
Occasional |
| 3 |
Frequent |
| 4 |
Common |
| 5 |
Abundant |
Qualitative variables
These are non numerical and descriptive; they have no order of preference and are not measured on a numerical scale or ranked in order of magnitude. These are described in terms of categories.
Example
- Dead or alive
- Shape of mould colonies : Round, flat, elongated
Summary
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Experimental design aspects
Control
Group
Variables
Measuring Variables
Sample
size
Replication
Errors
in ExperimentsWorking Scientifically
Observations
Observation Questions
Hypothesis Formation
Experimental Design
Aspects
Ethics
Types of Research
Data Analysis |
