T-test critical value table look-up


This page looks-up critical t-score values from the t score table to facilitate decisions about statistical significance.

Select the number of tails.

one tail two tails

Select the desired p value.

p = .10 p = .05 p = .01

*** Waiting for results ***


Statistical significance is a way of saying that the null hypothesis is unlikely to be true. These situations have probabilities that will be in the tails of the t-distribution. So where does the tail part begin? The critical value defines where statistical significance would begin.

For one-tailed tests (for a prediction of higher scores):

T-test decisions for one-tailed situations

For two-tailed tests:

T-test decisions for two-tailed situations

Obtained t-test scores that are more extreme than the tcritical value are statistically significant. If your calculated t score (tobtained) goes beyond tcritical, then p < .05 and the null hypothesis is rejected. In other words, your t score is out in the tail region and unlikely to occur by chance. Otherwise, when tobtained is less tcritical the p value is p > .05 and the null hypothesis is kept. These outcomes are in the middle (near t = 0) and are likely to occur by chance.

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