Because we want to including rounding during continuity correction to account for things discretized to certain values.
| Discrete | Continuous |
|---|---|
| P(X = 6) | P( 5.5 <= X <= 6.5) |
| P(X >= 6) | P (X >= 5.5) |
| P(X > 6) | P (X >= 6.5) |
basically “less than
continuity correction