Normal approximation to binomial distribution 

Continuity Correction Factor (+0.5 or -0.5).
Suppose that a and b are two integer values, where a is smaller than b.
P(X less than a) = P(X less than a - 0.5)
P(X less than or equal a) = P(X less than a + 0.5)
P(X more than a) = P(X more than a + 0.5)
P(X more than or equal a) = P(more than a - 0.5)
P(X between a and b) = P(X between a+0.5 and b - 0.5)
P(X from a to b) = P(X between a - 0.5 and b + 0.5)
P(X equal a) = P(X between a - 0.5 and a + 0.5)
I apologize again for my nasal voice. I was still having a flu when recording this video.