A finely tuned continuity correction
The role of the continuity correction of 1/2, when approximating discrete binomial probabilities with normal probabilities, is examined. It is shown that a substantial improvement is available, one that involves very little more computational effort (it can easily be performed on a pocket calculator), and gives big gains in accuracy. 1978 Kluwer Academic Publishers.
Cressie, N. A. (1978). A finely tuned continuity correction. Annals of the Institute of Statistical Mathematics, 30 (1), 435-442.