Data in this lesson take two primary forms: counts of organisms and intervals of time.   Potential targets for data modeling include: a) explicit representation of the sampling scheme and b) change over time.

1) How representative of the actual sample are the collected data? Students count the same plates, but report a wide range of results. Different methods of counting and estimation as well as counting mistakes (e.g., losing track) can affect overall error.

2) Is the sample representative of the actual culture? Students count one plate at each time point.   M ultiple samples at each time point would support a more accurate estimate of population size.

3) How do the data compare to the ideal doubling model? Although basic doubling can be used to model part of microbial population growth, in nature there are limits to this growth. For this reason, the doubling model does not precisely capture the pattern of growth.

4) An alternative model that describes the data better looks more like an S-shaped curve, sometimes called a logistic curve.