# Math Help - Sampling theory

1. ## Sampling theory

The standard deviation of the masses of articles in a large population is 4.55kg. If samples of size 100 are drawn from the population, find the probability that a sample mean will differ the true population mean by less than 0.8kg.

* the answer is 0.921, but i don't know what is the working.

2. Originally Posted by SakuraSky
The standard deviation of the masses of articles in a large population is 4.55kg. If samples of size 100 are drawn from the population, find the probability that a sample mean will differ the true population mean by less than 0.8kg.

* the answer is 0.921, but i don't know what is the working.
The difference between the sample mean and the population mean is a RV with an approximately normal distribution with zero mean and sd = 4.55/sqrt(100).

CB