Unfortunately, arsenic occurs naturally in some ground water.tarsenic occurs naturally in some ground water.$*$ A mean arsenic level of $=8\mathrm{.}0$ parts per billion $($ppb$)$ is considered safe foragricultural use. A well in Texas is used to water cotton crops. This well is tested on a regular basis for arsenic. A random sample of $31$ tests gave asample mean of x $=6\mathrm{.}9$ ppb arsenic, with s $=2,4$ ppb$.$ Does this information indicate that the mean level of arsenic in this well is less than $8$ ppb$?$Use a $=0\mathrm{.}01.$