Why is the strength of genetic drift inversely proportional to the population size?

Question

I saw a concept on the Internet that says "the strength of genetic drift is inversely proportional to the population size". I don't know why they are **inversely proportional**? Can somebody explain? Thank you all!

Answer 1

Genetic drift is a random change in allele frequency. If you have a small group of individuals, addition or loss of a single individual causes a larger proportional change in allele frequency than it would in a larger group. Mathematically, 1/100 is a much more significant proportion than 1/100,000. The larger population reduces the impact of the random change.