# The number of times a CI contains the true value: What distribution does this follow?

Suppose we repeat an experiment identically and independently 100 times. Each time we construct a 99% conﬁdence interval for $\mu$ via the t-distribution. Let X = the number of times the conﬁdence interval fails to contain the true value of $\mu$. The distribution of X is:

Normal with $\mu=0$ and $\sigma^2 = 1$, is this correct? Since in Normal, the mean should be zero and the variance is always one.

Since this is a t-distribution, it should be Normal. I thought another answer might suit it being Normal with $\mu = 99$ and $\sigma^2 = 0.99$

Could someone explain which one could be correct, if correct at all?

• Think about this, what values can $X$ take on? Can $X$ be negative? Can $X$ be a non-integer? – Cam.Davidson.Pilon Apr 19 '14 at 1:15
• @Cam.Davidson.Pilon So re-thinking about this, X can take on only integers that indicate where the CI succeeded or failed. It cannot be negative and must be an discreet variable. Since it's either success or failure, then this is a Binomial with $n=100$ and $p=0.01$, Does this make sense? – GivenPie Apr 19 '14 at 1:22
• So perfect you should write it as an answer yourself! – Cam.Davidson.Pilon Apr 19 '14 at 1:27