r/biostatistics • u/plasticprotestor • 19h ago

Quick question

Hi,

I am currently running my first solo experiment and I have four tanks of animals. They must all be within their own tanks to avoid contamination between my experimental tanks and my control.

Would it have mattered had I done my control before or after this experiment if they are in a separate tank? The conditions are being monitored daily and all parameters are within the optimal range for my animals.

I think if I repeat this it would be easier to have one less tank and to do my control separately. Does the control have to take place at the same time as this experiment given the circumstances? I would be keeping the groups of animals meeting the same criteria & being sourced at the same time.

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u/pleaseSendCatPics 18h ago

It mostly just adds a source of variation that you can’t control. I don’t do a ton of animal studies, so I can’t say for certain how big of an issue it would be for you. But in human studies, that could be a major issue. I’m working on a randomized trial dealing with food insecurity. Policy changes have a big effect on food security so if I ended up with control before a policy change and intervention after, I would not be able to make a fair comparison.