# Thread: Binomial or Geometric distribution?

1. ## Binomial or Geometric distribution?

Can someone please help me out with this. I've been trying for about forty minutes, but I'm not getting this. Trust me, I've done everything I can to try to look up strategies/tips on these types of problems, but it's not helping. I REALLY appreciate any assistance!

32% of employed women have never been married. Suppose you randomly select 10 employed women and determine marital history.

1) What is the random var X of interest here? Define X. Is X binomial, geometric, or normal?
2) If 10 employed women are selected at random, what is the prb that 2 or fewer have never been married?
3) What are the mean and standard deviation of X?
4) Find the prb that the # of employed women who have never been married is within 1 standard deviation of its mean.

70% of Americans are overweight. Suppose that a # randomly selected are weighed.

5) Find the prb that 18 or more of the 30 students in a class are overweight
6) How many Americans would you expect to weigh before you encounter the first overweight individual?
7) What is the prb that it takes more than 5 attempts before an overweight person is found?

Thank you so so so so much if you could help! I really appreciate it!

2. a binomial RV.. can you do 2,3 and 4?

3. I'm sorry, I'm really having trouble with this concept. For the first group of problems, I got that it's binomial.

p = 0.32 -- Never married
q = 1 - 0.32 = 0.68 = -- Married
n = 10

I just don't really know what to do from there (and defining X?).

The second group of problems is even worse for me.

4. You should read from your notes what binomial distribution is and how it is used.

1) X is binomial

2)$\displaystyle p = 0.32 \;\;\; 1 = 0.68\;\;\;n=10$

for a binomial $\displaystyle P(X=x) = \dbinom{n}{x} p^x (1-p)^{n-x}$. Using this, find

$\displaystyle P(X \leq 2) = P(X=0)+P(X=1)+P(X=2)$

3) mean and sd should be in you book.. its just plugging values of n and p into the formula of n and p..

I suggest you to look at your notes or read about Binomial Distribution to get a proper grasp.