# one or two tailed?

#### acarnle1

##### New Member
Ok, so i know when testing to determine if say a drug umproves some fuction, the null and alternate hypothesis would not be two tailed. But, if im not sure which signs to use, < or > when setting up my null and alternate hypothesis for this one problem i am setting up to solve for.
The question asks what my null and alternate hypothesis would be if i was to determine whether test subjects with a new treatment have a longer life span than that of the mean life span. Would this be set up null < #, and alternate >#, meaning i would have a one tailed upper critical?
Thanks=)

#### vinux

##### Dark Knight
The question asks what my null and alternate hypothesis would be if i was to determine whether test subjects with a new treatment have a longer life span than that of the mean life span. Would this be set up null < #, and alternate >#, meaning i would have a one tailed upper critical?
Thanks=)
The effective null hypothesis is null = #
alternate >#

check this also
http://en.wikipedia.org/wiki/Null_hypothesis & see the Directionality part