Solve this equation and find n.
So we have a weapon with probability of working succesfully. We test weapons and the stockpile is replaced if the number of failures is at least one. How large must n be to have ?
a)Use exact binomial
b)Use normal approximation
I know we can use ...
And then normalise this distribution to the standard normal form something like:
If that is correct I have to solve that for n,.... how?
Also I doubt that rewriting is smart...
[QUOTE=CSM;610438]Why is that?
Whenever you want to approximate a discrete distribution (i.e. your initial Binomial Distribution) by a continuous one (i.e. the Normal Distribution), you have to do a continuity correction - that is, the variable X in the Binomial distribution can take only the values 0, 1, 2, 3, ... (natural numbers)as the X in the Normal Distribution can take any REAL value above 0.
The continuity correction is "filling up" the gaps between 0,1, 2, ...
This is why P(X>=1) becomes P(X>0.5) ( the integer value 1 moves into a rectangle starting 0.5 until 1.5, the integer value 2 moves into a rectangle starting 1.5 ending 2.5, etc)