what is the difference between a two tailed and one tailed test 
a two tailed hypothesis test is designed to show whether the sample mean is significantly greater than or significantly less than the mean of a population the two tailed test gets its name from testing the area under both tails sides of a normal distribution a one tailed hypothesis test on the other hand is set up to show only one test that the sample mean would be higher than the population mean or in a separate test that the sample mean would be lower than the population mean 