MathCastle
Statistics & DataSuperchallengeBinomial and Geometric

Binomial and Geometric · Superchallenge problem

A fair coin is tossed nn times, nn even, and XX is the number of heads. With a continuity correction, P(X=n/2)P(X = n/2) is approximated by the normal area over an interval of width 11 centred at the mean, which is about 1σ2π\dfrac{1}{\sigma\sqrt{2\pi}} (the height of the normal curve at its peak), where σ\sigma is the SD of XX. Using this approximation, what is the smallest even nn for which P(X=n/2)<0.05P(X = n/2) < 0.05?