## OUTLIER CASES. IDENTIFICATION AND SIGNIFICANCE IN DATA ANALYSIS

By RAFAŁ WAŚKO (Predictive Solutions) In data analysis, it is important to identify unusual observations that are significantly different from the others. Such values, called outliers or outlier cases, can affect the results of statistical analysis and lead to...

## LOGISTIC REGRESSION

By WIKTORIA KORYGA (Predictive Solutions) In practice, the simplest and most commonly used type of regression is the linear regression model, whose parameters are estimated using the Least Squares Method. However, linear regression is only used to predict a continuous...

## GINI INDEX

By WIKTORIA KORYGA (Predictive Solutions) The Gini index is a measure of the concentration of a variable's distribution. In statistics it is commonly used to describe the concentration (unevenness) of the distribution of a random variable, while its most popular use...

## THE POWER OF A TEST

By RAFAŁ WAŚKO (Predictive Solutions) The power of a test is the probability of detecting a statistically significant effect when one actually occurs in the population under study. Without adequate test power, we may make a type II error, meaning that the analyst will...

## SKEWNESS AND KURTOSIS

By WIKTORIA KORYGA (Predictive Solutions) Kurtosis and skewness are measures of asymmetry that describe such properties as the shape and asymmetry of the distribution under analysis. They provide us with information on how the values of the variables deviate when...

## STUDENT T-TESTS

By RAFAŁ WAŚKO (Predictive Solutions) The Student's t-test group is used to compare two groups of results, measured by the arithmetic mean, against each other. WHAT DO THE T-TESTS TEST? These types of tests will be useful to us when we want to determine whether the...

## Pearson’s Chi-Square Test Of Independence

By RAFAŁ WAŚKO (Predictive Solutions) The chi-square test of independence is one of the most popular statistical tests. It is used to check whether there is a statistically significant relationship between two qualitative variables. It is based on comparing the...

## Customer Effort Score (NPS)

By RAFAŁ WAŚKO (Predictive Solutions) Customer Effort Score (CES), along with Net Promoter Score (NPS), and Customer Satisfaction (CSAT), is one of the key indicators related to clients' satisfaction. All these three indicators are intended to understand the moods of...

## CUSTOMER SATISFACTION INDEX (CSI)

By NATALIA GOLONKA (Predictive Solutions)   The Customer Satisfaction Index (CSI) is a method used in marketing to evaluate client satisfaction derived from products or services being provided by a company or organisation.Using a short questionnaire it is...

## Linear Regression

By RAFAŁ WAŚKO (Predictive Solutions) The main idea of regression is to predict the value of a dependent variable (otherwise known as predictor, explained variable) based on one or more independent variables (called predictors, explanatory variables). The simplest...