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

Here we consider comparing the statistic from two samples. we would compare the mean, population proportion and variance. The tests used would be the z test and the t- test. Some of the experiments would use independent samples. (members in both the samples are independent of each other)Difference in two means using z-statistic : according … Read more

Hypothesis is defined in dictionary.com as ‘a proposition assumed as a premise in an argument’. This post explores the various kinds of hypothesis in statistics and methods to test them. Research hypothesis : A statement that is considered the outcome of an experiment or test, before the experiment is undertaken.Statistical hypothesis : This is used … Read more

Inferential statistics is the term given to the branch of statistics that uses the information from the sample to infer the information about the population. For example, given a sample mean , the population mean (also called a parameter) can be determined using inferential statistics. Estimating population mean – Let us first look at estimating … Read more

It is necessary to understand sampling techniques before data for a sample is gathered for analysis. Some of the terms that are important arePopulation – This is the complete set under consideration. For example a survey of food choices for a country might consider all citizens of the country.Frame – frame is the population where … Read more