Step 3 - Determining Deviations

Next, in this case study, we will calculate how much the observed phenotypes differed from those that were  expected. Put together a table such as the following, where the expected numbers are subtracted from the observed for each phenotype class. This difference is called the deviation (Table 1).

Table 1: Organizing data into a table.
Class Observed (O) Expected (E) Deviation (O-E)
Resistant 141 147.75 -6.75
Susceptible 56 49.25 +6.75