## Binomial Probability (Elementary Statistics)

Hi, I was hoping someone could explain this to me. I've tried online tutoring, and honestly it doesn't seem like they know what their doing. My e-text book isn't much help and I've watched a few hours worth of YouTube tutorials. Now, I know I'll probably get told to use my TI-84 but I'm supposed to know how to do this on paper.

Problem:

Twenty-six percent of psychologists say that elderly adults have higher chances of being depressed. You randomly select 50 elderly adults and ask if they feel depressed.

a. Find the probability that the number who say elderly adults have higher chances of being depressed is exactly 10.

My Solution:

Step 1.

I like to find all the variables first.

n=50
x=10
p=0.26
q=1-0.26=.74

Step 2.

I use this equation:

I then substitute the known variables, and solve for nCr first.

I cancelled the 40's first.

I understand that e means exponent but I'm not sure what to do here?

Is this correct?

so nCr=1389558608/38800= 382.9251014