Should the formula for test statistic have an absolute value? I have been given a formula for calculating a t test statistic as 
$$t_{n-1} = \frac{ \bar{x}- \mu_0}{\frac{S}{\sqrt{n}}} $$
Where $\bar{x}$ is the sample mean, $\mu_0$ is the hypothetical true mean, $S$ is the sample standard deviation and $n$ is the sample count.
But when I plug my values in, the outcome is negative.
I don't see how to look up a negative value on the T-table.
Should I be taking the absolute value?

The support of $\mathrm t$ distribution is $\mathbb R. $ So, it is still a legit case if $t_{n-1}<0.$ And don't forget the probability curve is symmetric about $0.$
