There are many sources of variability inherent in lettuce seed bioassays. The following table outlines a few of these sources and how they might affect your experiments. This is the kind of decision that each experimenter can make, but in order to compare the results of your experiments with those of other scientists, you want to clearly state what decisions you have made. Judgement is often important in scientific measurements.
Scientists continually have to be on the lookout for sources of bias in their experiments.
They are much more likely to get their results published and to continue receiving funding if they get good results from their experiments.