This is a part of my lecture note.
To test whether $\beta_2 \le 0$ at the 5% level of significance:
Hypothesis: $H_0 : \beta_2 =0$ and $H_1 : \beta_2 >0$
I don't understand $H_0: \beta_2 =0$ instead of $\beta_2 \le 0$.
My lecturer said it is because the worst case of $\beta_2$ is when it is equal to 0, but I don't really get what it means.