Should observers switch sides when conducting aural surveys at frog ponds?

Reply Wed 18 Mar, 2020 09:19 pm
I have been doing some research where two oberservers will stand in the middle of a frog pond facing opposite directions listening for frog calls (from 3 different species) within their half of the area. They record the number of individuals they hear calling of each species, and also their approximate location. We aim to compare this information to data collected from audio recorders paced around the pond in an array. We have done 7 surveys using this method where the observers have always stood back-to-back in the same position in the pond, facing the same direction every time. However, we are now replacing one of the oberservers with a different person. Would it be statistically better to continue the previous method of the two observers always facing the same way in the pond, or should we start randomising the direction faced/half of the pond being observed by each person? If we randomise the direction faced, would we still be able to compare this data to the previous survey data we have collected? We are probably only able to complete 4 or so more surveys (maybe 6, but this is unlikely).
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Reply Thu 19 Mar, 2020 06:30 am
Think of it in terms of independent variables. Right now, for each data point, you have 2 observers, one positioning so 2x1. You need to have a third observer, so now you will be 3x1. If you change the positioning, you will have 3x2 or more and you won't be able to get information about observer one in position 2. This is drastically increasing the number of data points you need. IMO, stick with your original experimental design.

Of course in retrospect if you believe your original design was faulty, by all means scrap that and start again.
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