We have two measures of a distribution: Central tendency and dispersion. The mean is a measure of central tendency. It measures the average length of the bolt. The variance is a measure of dispersion. It measures how the lengths of the bolts are distributed around the mean value.
A lower variance means that the ...
Explains in simple english (for easy understanding) the meaning of mean, variance and confidence interval. No mathematics or formula is used to keep it simple and specific.