# One-Tailed Test

- A statistical test in which the critical area of a distribution is one-sided so that it is either greater than or less than a certain value, but not both. If the sample that is being tested falls into the one-sided critical area, the alternative hypothesis will be accepted instead of the null hypothesis. The one-tailed test gets its name from testing the area under one of the tails (sides) of a normal distribution, although the test can be used in other non-normal distributions as well.
An example of when one would want to use a one-tailed test is in the error rate of a factory. Let’s say a label manufacturer wants to make sure that errors on labels are below 1%. It would be too costly to have someone check every label, so the factory selects random samples of the labels and test whether errors exceed 1% with whatever level of significance they choose. This represents the implementation of a one-tailed test.

*Investment dictionary.
Academic.
2012.*

### Look at other dictionaries:

**one-tailed test**— a hypothesis test (q.v.) in which the critical region is one tail of the distribution of the test statistic and the null hypothesis is tested against a one sided alternative that includes deviations from the null hypothesis only in one direction … Medical dictionary**one-tailed**— ¦ ̷ ̷ ˌ ̷ ̷ adjective also one tail : being a statistical test for which the critical region consists of all values of the test statistic greater than a given value or less than a given value but not both compare two tailed herein * * * adj.… … Useful english dictionary**one-tailed**— also one tail adjective Date: 1947 being a statistical test for which the critical region consists of all values of the test statistic greater than a given value or less than a given value but not both compare two tailed … New Collegiate Dictionary**one-tailed**— adjective Statistics denoting a test for deviation from the null hypothesis in one direction only … English new terms dictionary**Two-tailed test**— The two tailed test is a statistical test used in inference, in which a given statistical hypothesis, H0 (the null hypothesis), will be rejected when the value of the test statistic is either sufficiently small or sufficiently large. This… … Wikipedia**Two-Tailed Test**— A statistical test in which the critical area of a distribution is two sided and tests whether a sample is either greater than or less than a certain range of values. If the sample that is being tested falls into either of the critical areas, the … Investment dictionary**Student's t-test**— A t test is any statistical hypothesis test in which the test statistic follows a Student s t distribution if the null hypothesis is supported. It is most commonly applied when the test statistic would follow a normal distribution if the value of … Wikipedia**Fisher's exact test**— is a statistical significance test used in the analysis of categorical data where sample sizes are small. It is named after its inventor, R. A. Fisher, and is one of a class of exact tests. Fisher devised the test following a comment from Muriel… … Wikipedia**Welch's t test**— In statistics, Welch s t test is an adaptation of Student s t test intended for use with two samples having possibly unequal variances. As such, it is an approximate solution to the Behrens–Fisher problem.FormulasWelch s t test defines the… … Wikipedia**Binomial test**— In statistics, the binomial test is an exact test of the statistical significance of deviations from a theoretically expected distribution of observations into two categories.For example, suppose we have a board game that depends on the roll of a … Wikipedia