Logistic regression is a statistical method that predicts the probability of one of two outcomes, such as “buys” or “does not buy”. It weights the input features and converts their sum into a value between 0 and 1 using an S-shaped function. Because the weights are easy to interpret, it is widely used in credit scoring, medicine and marketing, often as a solid baseline for more complex models.
Linear regression is a statistical method that describes the relationship between a target variable and one or more predictors using a straight line or plane. The coefficients are usually chosen to minimise the sum of squared deviations. The method is easy to understand and interpret: for example, it can estimate how much revenue rises when the advertising budget increases by €1,000. It reaches its limits with non-linear relationships.
A classifier is a model or method that assigns inputs to one of several predefined categories. Classic variants such as decision trees or naive Bayes are trained on labelled examples; language models can also sort texts based on a description of the categories. Typical uses include spam detection, sorting customer enquiries by topic and categorising receipts. Quality is measured with metrics such as accuracy, precision and recall.
Log loss (logarithmic loss) measures how well the predicted probabilities of a classification model match the actual outcomes. Confident but wrong predictions are penalised particularly heavily; a value close to zero indicates well-calibrated forecasts. Example: if a model gives a 95% churn probability for a customer who stays, the log loss rises sharply. Mathematically it is the same as binary cross-entropy.
Naive Bayes is a family of simple classification methods based on Bayes’ theorem. They are called “naive” because they assume all features are independent of one another, which is rarely true in practice but often still produces good results. The methods are fast, need little training data and are particularly well suited to text. A classic example is the spam filter that sorts emails based on typical words.
