Exploration and description

Mortality

We need to heed this message. When some values are small we need to adjust the formula for a Chi² test by incorporating the value 0.5 as follows:

Chi² = Sum [(|Observed - Expected| - 0.5)²/Expected]

Calculating by hand we find that the Chi² value reduces to 2.42; this is well below the significance level.

Thus, although there was a trend to suggest that Saccharomyces cerevisiae helped to reduce mortality, the levels of mortality observed in this study were too low to detect statistical significance.