(Solved): A certain type of thread is manufactured with a mean tensile strength of \( 83.1 \) kilograms and a ...

A certain type of thread is manufactured with a mean tensile strength of \( 83.1 \) kilograms and a standard deviation of \( 7.2 \) kilograms. How is the variance of the sample mean changed when the sample size is (a) increased from 81 to 256? (b) decreased from 324 to 64 ? (a) The sample variance for \( n=81 \) to for \( n=256 \) (Type integers or decimals. Do not round.)