When would you use a one-tailed rather than a two-tailed t-test when c

When would you use a one-tailed rather than a two-tailed t-test when checking significance levels?

What will be an ideal response?

ANSWER

You would use a one-tailed test when the sign of the variable is important. That is, if you only want to know if the independent variable has a statistically significant effect on the dependent variable, a two-tailed test should be used. If direction of effect is important, then a one-tailed test should be used.