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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
Measuring variables
Sample
size
Replication
Errors
in ExperimentsWorking Scientifically
Observations
Observation Questions
Hypothesis Formation
Experimental Design
Aspects
Ethics
Types of Research
Data Analysis |
