Geometric Distribution: suppose 20% of herd is infected

Suppose that 20% of a herd of cows is infected with a perticular disease.

1) What is the expected number of cows you would need to inspect to find one that has the disease?
My guess is twenty??

2) Identify the variable of interest. X=?
I think that X= the number of cows checked before an infected one is found

3)What is the probability that the first diseased cow is the third cow tested?
I do not know how to do this one without an n... i know that the p is .20

4) What is the probability that 6 or more cows would need to be tested until a diseased cow was found?

5)Construct a probabilty distribution table for X (up through X=5)
I think i usegeometcdf in my calculator but i dont know how...

Re: Geometric Distribution

Your 2 posts are populated with numerous (I think)'s and (I guess)'s and "calculator uncertainties":
I suggest you clear a few of those with your teacher's help; we can't conduct a classroom here.