In a survey of $150$ publicly$-$traded companies, the average price$-$earnings ratio was $18\mathrm{.}6$ with a standard deviation of $8\mathrm{.}9.$ When testing the hypothesis $($at the $5\%$ level of significance$)$ that the average energy use has decreased from the past value of $16\mathrm{.}5,$ what is the critical value? $($please round your answer to $2$ decimal places$)$