Is the Null Hypothesis ... ?

If the alternative hypothesis is mu>13 then what is the null?

Is it a) mu<=13 or b) mu=13

I've seen both a) & b) so what's the rationale for each one?


Cookie Scientist
It's conventionally (a) mu<=13. The rationale is that it is the negation of mu>13. I haven't seen (b) so couldn't say much about a rationale for that.