one tailed and two tailed


hi again
suddenly I've become confused about one-tailed and two-tailed.
can someone please explain to me what is meant by one-tailed t test
it is because of the response from the research question, yes or no
and then if it is a two-tailed test, its yes, no and maybe.

love satchi

Avatar for sneaks

use a two tailed tests if you think there will be no difference between groups

use one tailed if you are saying that your results will come out in a particular direction e.g. one group scoring higher than another, a positive correlation etc.


thanks Sneaks
:-) :-) :-)
love satchi


just to add to this, in psychology we use two tailed tests when you don't know the direction of the relationship e.g. whether higher scores on one variable result in higher or lower scores on another, or which group is most likely to show higher scores etc. you would use one tailed tests when you have a good basis for believing that the effect will be in a specific direction.

hope that helps


hi purplecat
thanks very much, yes its helpful
then I would be using two-tailed test
love satchi


good luck with it all. i'm in the middle of my own analysis at the moment, and it's driving me crazy! hope yours goes more smoothly!