How to calculate a p-value for a sample size


New member
Apr 13, 2021
Hi everybody.
Here is a problem I am having difficulty with. I think it should be simple but I cannot find the solution online.
Given that 25% of families have a fish tank, John asked 40 of his friends and only 10% of them had a fish tank. What is the p value?

I am guessing the question is what is the probability of having 4 (or fewer) families having a fish tank out of a sample of 40 families.
Tanks in advance :)