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Horticulture 1000
HT1011 - Practical investigations - Designing investigations
Collecting and recording data

Designing investigations

Why carry out investigations?

Growers and plant breeders often make decisions to try to improve productivity and maintain sustainable land use. The results of trials or investigations can help growers and plant breeders to make these decisions.

Observational trials of medicinal herbs
Observational trials of medicinal herbs

Investigations are carried out to test an idea to see if it is worthwhile putting into practice on a larger scale.

A practical investigation is made up of three parts:

  • planning
  • collecting, recording and processing data
  • a written report that includes interpretation of results and a conclusion.


A workable plan will contain enough detail so another person could repeat the investigation in exactly the same way you carried it out.

A plan will include:

  • an aim: this is what you want to find out
  • a hypothesis: a prediction of what you think will happen
  • the equipment: a list of all the gear and plant material that will be needed to carry out the investigation
  • the independent variable: the condition you will change
  • what will be measured and how the variable will be changed
  • a list of variables that will remain the same. A fair test has variables controlled by you. Only one variable is changed, so that it is the only factor affecting the results. If you were testing the effect of temperature on germination then all the other variables such as light, oxygen, and water would be kept the same and the only variable that would change would be the temperature
  • the control. This is used as a comparison in an investigation so the effect of changing one variable is shown. In the temperature investigation example seeds sown at room temperature would be the control. You could then compare the results of the seeds that were in a warm environment to those that weren’t
  • a reasonable sample size to ensure reliable results. If you use only one plant or seed in an investigation your results will not be reliable. The number you use will depend on the space available and the type of investigation. Twenty seeds for each treatment in the example of a temperature investigation would be adequate. To make sure the results are accurate, the investigation needs to be repeated at least once
  • a method that is a detailed list of step-by-step instructions. It may include descriptive diagrams.

What's next?

Go to: 2 Collecting and recording data.

Collecting and recording data