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  2. One- and two-tailed tests - Wikipedia

    en.wikipedia.org/wiki/One-_and_two-tailed_tests

    A two-tailed test applied to the normal distribution. A one-tailed test, showing the p-value as the size of one tail. In statistical significance testing, a one-tailed test and a two-tailed test are alternative ways of computing the statistical significance of a parameter inferred from a data set, in terms of a test statistic. A two-tailed test ...

  3. Sign test - Wikipedia

    en.wikipedia.org/wiki/Sign_test

    alternative =indicates the alternative hypothesis and must be one of "two.sided", "greater" or "less" conf.level = confidence level for the returned confidence interval. Examples of the sign test using the R function binom.test The sign test example from Zar [5] compared the length of hind legs and forelegs of deer. The hind leg was longer than ...

  4. Z-test - Wikipedia

    en.wikipedia.org/wiki/Z-test

    First, estimate the expected value μ of T under the null hypothesis, and obtain an estimate s of the standard deviation of T. Second, determine the properties of T : one tailed or two tailed. For Null hypothesis H 0: μ≥μ 0 vs alternative hypothesis H 1: μ<μ 0, it is lower/left-tailed (one tailed).

  5. Statistical significance - Wikipedia

    en.wikipedia.org/wiki/Statistical_significance

    As a result, the null hypothesis can be rejected with a less extreme result if a one-tailed test was used. [40] The one-tailed test is only more powerful than a two-tailed test if the specified direction of the alternative hypothesis is correct. If it is wrong, however, then the one-tailed test has no power.

  6. Test statistic - Wikipedia

    en.wikipedia.org/wiki/Test_statistic

    If there is interest in the marginal probability of obtaining a tail, only the number T out of the 100 flips that produced a tail needs to be recorded. But T can also be used as a test statistic in one of two ways: the exact sampling distribution of T under the null hypothesis is the binomial distribution with parameters 0.5 and 100.

  7. Null hypothesis - Wikipedia

    en.wikipedia.org/wiki/Null_hypothesis

    A one-tailed hypothesis (tested using a one-sided test) [2] is an inexact hypothesis in which the value of a parameter is specified as being either: above or equal to a certain value, or; below or equal to a certain value. A one-tailed hypothesis is said to have directionality. Fisher's original (lady tasting tea) example was a one-tailed test ...

  8. Welch's t-test - Wikipedia

    en.wikipedia.org/wiki/Welch's_t-test

    A two-tailed test, in which the two population means are equal; or A one-tailed test , in which one of the population means is greater than or equal to the other. The approximate degrees of freedom are real numbers ( ν ∈ R + ) {\displaystyle \left(\nu \in \mathbb {R} ^{+}\right)} and used as such in statistics-oriented software, whereas they ...

  9. Student's t-test - Wikipedia

    en.wikipedia.org/wiki/Student's_t-test

    A two-sample location test of the null hypothesis such that the means of two populations are equal. All such tests are usually called Student's t -tests , though strictly speaking that name should only be used if the variances of the two populations are also assumed to be equal; the form of the test used when this assumption is dropped is ...