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Chapter 3: Experimental design - Setting up a fair trial


Looking at a feed trial example

The fundamental nature of a successful scientific trial is that it allows you to make comparisons based on consistent data that has been collected and recorded in a systematic way. These processes ensure that the data is:

  • accurate
  • reliable
  • valid.

Have a look at the information to be gathered for a feed trial involving two different types of feeds. These trials are to be run concurrently, that is, at the same time and under the same conditions (except different feeds are given), to determine which feed is more efficient. Which elements are constants or variables (independent and dependent) for both trials?

If you can't access the interaction below, you can use this alternative instead.

Identified trial elements constant
 Independent
Variable		 Dependent
Variable
 Answer
Stock number


constant
Species


constant
Ponds


constant
Time period


constant
Interval (e.g. daily)


constant
Type of feed given to stock


independent
variable
Stock weight


dependent
variable
Conditions
e.g. water quality and quality of feed.



constant
Formulas for calculating:
  • mortality rates


constant
  • daily survival rate


constant
  • food conversion ratio (FCR)


constant
  • average FCRs


constant
Recording information


constant

How did you go?

Remember, the complexities of setting up a fair trial are quite difficult to grasp, particularly when trying to determine the independent and dependent variables. It is crucial that you have a clear understanding of both constants and variables before you can correctly apply them to an experiment.

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