Use a one-tailed t-test if you want to test whether this mean (or difference in means) is greater/less than the pre-set value.įormulas for the test statistic in t-tests include the sample size, as well as its mean and standard deviation. Use a two-tailed t-test if you only care whether the population's mean (or, in the case of two populations, the difference between the populations' means) agrees or disagrees with the pre-set value.
#P value for the indicated hypothesis test calculator how to#
These next steps will tell you how to calculate the p-value from t-test or its critical values, and then which decision to make about the null hypothesis.
So, you've decided which t-test to perform. The change in blood pressure in patients before and after administering some drug.The change in student test performance before and after taking a course.In particular, you can use this test to check whether, on average, the treatment has had any effect on the population. This test is sometimes referred to as an independent samples t-test, or an unpaired samples t-test.Ī paired t-test is used to investigate the change in the mean of a population before and after some experimental intervention, based on a paired sample, i.e., when each subject has been measured twice: before and after treatment. The average difference in the results of a math test from students at two different universities.The average difference in weight gain in two groups of people: one group was on a high-carb diet and the other on a high-fat diet.In particular, you can use this test to check whether the two groups are different from one another. The average weight of people from a specific city - is it different from the national average?Ĭhoose the two-sample t-test to check if the difference between the means of two populations is equal to some pre-determined value, when the two samples have been chosen independently of each other.The average volume of a drink sold in 0.33 l cans - is it really equal to 330 ml?.Your choice of t-test depends on whether you are studying one group or two groups:Ĭhoose the one-sample t-test to check if the mean of a population is equal to some pre-set hypothesized value.
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