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Use/Abuse Principles How To Related
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Just a note

In this example we have ignored random variation in the number of files caught, but consider day-to-day differences in catches, differences between sites, and differences due to trap type.

We noted in Unit 2, study designs are used to separate the sources of variation that affect your results.

If we did not use a suitable experimental design we could not know if the trap-type which caught most only did so because happened to be in the best site. Randomly positioning traps would reduce such bias, but only average - in practice this approach requires very much more work because we it requires we use many more traps, and operate them for many more days. We explore the reasoning behind the crossover design, and other study designs, in Unit 7.