Unfortunately, arsenic occurs naturally in some ground water. A mean arsenic level of= 8.0parts per billion (ppb) is considered safe for agricultural use. A well in Texas is used to water cotton crops. This well is tested on a regular basis for arsenic. A random sample of41tests gave a sample mean ofx=6.9ppb arsenic, withs=2.8ppb. Does this information indicate that the mean level of arsenic in this well is less than 8 ppb? Use= 0.01.

What is the value of the sample test statistic? (Round your answer to three decimal places.)