A hint to get started
Find a probability within one standard deviation of a binomial mean
A box contains two red balls among seven balls. A ball is drawn randomly, its colour noted, then returned and mixed with the others. Repeat 50 times.
(i) Find the expected red count μ and standard deviation σ.
(ii) Find .
CJC · Lecture · Example 9
Use np for the mean and square-root of np(1−p) for standard deviation.
Keep exact bounds until you identify the included integers.