Anti-E has been confirmed with an acceptable probability. There are more than three positive cells and three negative cells (meeting the minimum p value of 0.05).

**Online p value calculator**

See this online tool for calculating p values - Enter values as follows:

- Change
*Outcome 1*to*negative*and*Outcome 2*to*positive* - Change
*Group 1*to*antigen-neg (e.g., K-)*and*Group 2*to*antigen-pos (e.g., K+)* - The 2 x 2 table would look like this (hypothetical example):

Negative | Positive | |

K- | 9 | 0 |

K+ | 0 | 1 |

- Choose Fisher's exact test
- Use a
**one tailed test -**A one-tail p value is appropriate only when previous data or common sense tell you that a difference, if any, can only go in one direction. Obviously, with antibody identification, we expect cells that are antigen-positive to react (and vice versa). - Hit the
*calculate*button.

**Caution #1: **Statistical calculations do not substitute for carefully examining serologic test results. It is critical to consider p values as just another tool. If acceptable, they provide additional converging evidence to support the conclusion regarding which antibody has been identified.

**Caution #2: ** With complex antibody combinations, some blood banks prefer a minimum p value of 0.01 as an added measure of probability.