Unbiased estimator

Imagine you want to know how tall a group of kids are. You can't ask all of them, so you pick some at random and measure them. The average height of those kids is an estimate of the average height of the whole group.

But what if you only measured the tall kids or only measured the short kids? Then your estimate would be wrong. This is where an unbiased estimator comes in. An unbiased estimator is like a fair rule for picking which kids to measure. It doesn't favor tall or short kids, but picks a random sample from the whole group. This way, your estimate will be more accurate and closer to the actual average height of the group.

In more technical terms, an unbiased estimator is a statistical method that produces estimates without systematically favoring one outcome or another. It doesn't over or underestimate the true value, but instead gives a fair estimate based on random samples.