# Binomial distribution

#### AStudent

##### New Member
Okay, I have two questions that maybe one of you could check for me, to see if I am right. I would greatly appreciate it.

Question 1:
A teacher interviews 15 students in a class of 200 to estimate the proportion of students who expect to obtain a "C" or better in the class as a grade. Is this a binomial experiment? Does the underlying variable follow the binomial distribution?

I think that it is a binomial experiment, because one would need it to have a fixed number of trials, independence, an outcome of 2 categories, and the probabilities remain consistent.
It does have a fixed number of trials (15), and the grades are independent of each other, and there are 2 categories (C or better / less than a C).
Am I correct in thinking this way? I would assume the variable follows this distribution.

Question 2:
A biologist randomly selects 10 portions of water, each equal to 0.1 cubic cm in volume, from a local reservoir and counts the number of bacteria in each portion. The biologist totals the number of bacteria for these 10 portions to obtain an estimate of the number of bacteria per cubic centimeter present in the reservoir. Is this a binomial experiment?

I do not think that this is a binomial experiment, since there are not two final categories of outcomes. Is this correct, or do I have to add them up and/or do something funky?

Thanks for any help of advice!