what you have given is a number
$(5/16 + 11/16)^4$
This isn't a distribution.
Can you repost what you actually mean?
HI; lets say I have a bistribution of (a + b)^4 where a = 5/16 and b = 11/16. what is the mean and standard deviation of the distribution? mean = na = 4*5/16 = 1.25 (that the mean of a) there must be a seperate mean for b? and seperate variances and standard deviations I assume?