Recently I was surprised to find a difference between two methods of
calculating a ratio during an experiment. Each animal has two measures
taken repeatedly over time. The ratio is of the two measures. I could
take the ratio at each time point, and then average the ratios to get
my animal ratio. Alternatively, I could average each of the two
measures and then form a ratio of the two averages, again getting my
animal ratio. The second method consistently gets a higher ratio than
the first method. Why would this occur? The second method is standard
in my literature base.
