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goodness of fit tests to a normal goodness of fit tests to a normal

Sin categoría / Statistics

Behind the scenes

Shapiro-Wilk and Kolmogorov-Smirnov tests are the most commonly used contrast tests to check the goodness of fit to a normal distribution of our data. Its implementation is described step by step and its equivalence in graphical methods such as the theoretical quantile graph and the cumulative density function graph.

07/16/2024

Sin categoría / Statistics

The vanishing hitchhiker

The p curve focuses on the significant p values of the primary studies of a meta-analysis and allows us to estimate, in addition to publication bias, whether there may be a real effect after the study, what its magnitude is, and whether there is suspicion of improper practices by researchers to obtain statistically significant values.

06/25/2024

Sin categoría / Statistics

Percy Fawcett and the Lost City

When multiple hypothesis tests are performed, the probability of committing a type 1 error increases, increasing the risk of detecting false positive effects. The false discovery rate allows to limit the probability of type 1 error when the number of contrasts is very high, also allowing to control the risk of making type 2 errors and failing to detect true positives.

06/04/2024

Sin categoría / Statistics

The tree and the labyrinth

A decision tree is a machine learning model that is used to estimate a target variable based on several input variables. This target variable can be either numerical (regression trees) or nominal (classification trees). The methodology for constructing decision trees for regression and classification is described, as well as their interpretation.

05/21/2024

Sin categoría / Statistics

The polysemy of Q

Cochran's Q is a widely used measure to detect heterogeneity between primary studies in a meta-analysis. Its statistical properties and hypothesis testing are reviewed. Finally, other measures calculated from this value are described, such as the I2 statistic and the H2 statistic, frequently used to quantify the intensity of heterogeneity between studies.

04/16/2024