T-Test:Problem : A swimming instructor wants to prove that the swimming speed of an athlete increases if the athelete performs some specific exercises before the swim. He undertakes an experiment with 16 participants and randomly assignes 8 participants to each team. For team A he recommends some common exercises and for team B he recommends … Read more

It is often confusing to decide on which statistic to use at what point. Also researchers need to be careful that the statistics they present does truly apply in the context of the problem. Statictics can be misleading and probably incorrect if used outside the boundaries set by its assumptions. In this post we analyse … Read more

The earlier posts on inferential statistics show methods that work on data whose population parameters and distribution are known. However, there are cases where the population parameters are not known. In such cases, no assumption can be made about the population statistics and hence parametric methods cannot be used. In such cases there are certain … Read more

Polynomial Regression: First order regression models contain predictors that are single powered. Polynomial models have one or more predictors having a power of more than one. A quadratic model has a predictor in the first and second order form.Since the constants are linear, the variable x1 squared can be recoded to x2 and then the … Read more

Two very important tests in statistical analysis are the t-test and the f-test. However, some confusion may arise for a new user as to the difference between the two tests. In this post I will try and present the difference between the two tests and when each should be used. But before we understand the … Read more

Simple regression deals with predicting a dependent variable using an independent variable using a linear regression equation. In multiple regression analysis there are more than one independent variables or at least one non linear independent variable. Multiple Regression Model :The multiple regression model is of the form.where y = the value of the dependent variable.beta0 … Read more

Introduction: In many situations, a relationship between two variables needs to be analysed. For example, a car manufacturer would like to know whether the number of cars bought in the city is related to the average household income in the city, or a sales manager would like to know if the sales revenue is dependent … Read more

Chi square tests, namely chi-square goodness of fit test and chi-square test of independence, are used to analyse data that are a frequency distribution of discrete variables. Consider for example, a wine cellar that has four different categories of wine, a frequency distribution of the four varieties of wine can be analysed by such tests.Chi-Square … Read more

Design of experiments : An experimental design is used to test a hypothesis by modifying one or more variables. The variables may be dependent or independent. Independent variables may be a treatment variable (can be modified) or classification variable (characteristic of the experimental factors, present prior to the experiment and is not modified during the … Read more