Category Statistics

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.

Manuel Molina
04/16/2024

Sin categoría, Statistics

The Palace of Probabilities

With small sample size, the variance of the Pearson’s coefficient increases, decreasing the precision of its estimates. The use of Fisher's z helps to stabilize the variance and obtain more precise estimates in meta-analyses whose outcome measure is a correlation, and when the sample of primary studies is small.

Manuel Molina
02/27/2024

Epidemiology, Statistics

The art of resignation

The procedure for choosing the cut-off point for a diagnostic test is reviewed. To decide this threshold, which is influenced by the characteristics of the model and the clinical scenario in which it will be applied, we will take into account the sensitivity and precision of the test for each possible cut-off point. The precision enrichment ratio will be useful in cases with a large imbalance between the two diagnostic categories.

Manuel Molina
01/30/2024

Sin categoría, Statistics

An epic dance

Multiple regression regularization (shrinkage) techniques can be very useful to address collinearity or overfitting problems. In addition, they can be used to select the independent variables and reduce multidimensionality, achieving more robust and easy-to-interpret models. Ridge, lasso and elastic network regression techniques are described.

Manuel Molina
12/05/2023

Sin categoría, Statistics

The paradox of the air

The parameters that report on the quality of a multiple logistic regression model and that are usually provided by the statistical programs with which they are carried out are reviewed. Emphasis is placed on the goodness of fit, the predictive capacity and the statistical significance of the model.

Manuel Molina
09/25/2023