#### week #9 – Overdispersion

In discrete response models, overdispersion occurs when there is more correlation in the data than is allowed by the assumptions that the model makes.

Comments Off on week #9 – Overdispersion

#### Week #8 – Confusion matrix

In a classification model, the confusion matrix shows the counts of correct and erroneous classifications.  In a binary classification problem, the matrix consists of 4 cells.

Comments Off on Week #8 – Confusion matrix

#### Week #7 – Multiple looks

In a classic statistical experiment, treatment(s) and placebo are applied to randomly assigned subjects, and, at the end of the experiment, outcomes are compared.

Comments Off on Week #7 – Multiple looks

#### Week #6 – Pruning the tree

Classification and regression trees, applied to data with known values for an outcome variable, derive models with rules like "If taxable income <\$80,000, if no Schedule C income, if standard deduction taken, then no-audit."

Comments Off on Week #6 – Pruning the tree

#### Week #5 – Features vs. Variables

The predictors in a predictive model are sometimes given different terms by different disciplines.  Traditional statisticians think in terms of variables.

Comments Off on Week #5 – Features vs. Variables

#### Week #4 – Logistic Regression

In logistic regression, we seek to estimate the relationship between predictor variables Xi and a binary response variable.  Specifically, we want to estimate the probability p that the response variable will be a 0 or a 1.

Comments Off on Week #4 – Logistic Regression

#### Week #3 – Prior and posterior

Bayesian statistics typically incorporates new information (e.g. from a diagnostic test, or a recently drawn sample) to answer a question of the form "What is the probability that..."

Comments Off on Week #3 – Prior and posterior

#### Week #2 – Permutation test

Consider two (or more) samples subjected to different treatments.  A permutation test assesses whether,

Comments Off on Week #2 – Permutation test

#### Week #1 – Quasi-experiment (revisited)

One avid reader took issue with a recent definition of "quasi experiment."  I had defined it

Comments Off on Week #1 – Quasi-experiment (revisited)