probittianalyysillä

Probittianalyysi, or probit analysis, is a statistical method used to analyze the relationship between a continuous predictor variable and a binary outcome variable. It is particularly useful when the outcome variable is dichotomous, meaning it can take on only two values, such as "yes" or "no," "success" or "failure," or "alive" or "dead." The method estimates the probability of the outcome occurring as a function of the predictor variable.

The core of probit analysis lies in the assumption that the probability of the outcome is related to the predictor variable through a cumulative normal distribution function. This means that as the predictor variable increases, the probability of the outcome also increases, but at a decreasing rate, following the characteristic S-shape of a normal distribution's cumulative density function.

Probit analysis is commonly employed in fields such as toxicology, where it is used to determine the dose of a substance that produces a specific response in a population, and in econometrics, to model binary choices such as whether a consumer buys a product or not. The model estimates coefficients that represent the change in the z-score of the normal distribution for a one-unit increase in the predictor variable. These coefficients can then be used to predict the probability of the outcome for different values of the predictor.