T Test, Chi-Square Test, Correlation, ANOVA, Regression, Nonparametric Tests,
When running correlations in SPSS, we get the significance levels as well. In some cases, we don’t want that: if our data hold an entire population, such p-values are actually nonsensical. For some stupid reason, we can’t get correlations without significance levels from the correlations dialog. However, this tutorial shows 2 ways for getting them anyway. We’ll use adolescents.sav throughout. Correlation Table as Recommended […]
This tutorial shows how to draw a regression line in SPSS. We encourage you to follow along by downloading and opening job_performance.sav, part of which are shown below. Our data basically just hold job performance scores and IQ, motivation and social support which -supposedly- contribute to job performance. The meaning of our variables is seen under variable view, […]
Running a basic multiple regression analysis in SPSS is simple. For a thorough analysis, however, we want to make sure we satisfy the main assumptions, which are linearity: each predictor has a linear relation with our outcome variable; normality: the prediction errors are normally distributed in the population; homoscedasticity: the variance of the errors is constant in the population. […]
Correlation B Coefficients Intercept Regression Residuals R-Square Simple linear regression is a technique that predicts a metric variable from a linear relation with another metric variable.Remember that “metric variables” refers to variables measured at interval or ratio level. The point here is that calculations -like addition and subtraction- are meaningful on metric variables (“salary” or […]
Multiple regression is a statistical technique that aims to predict a variable of interest from several other variables. The variable that’s predicted is known as the criterion. The variables that predict the criterion are known as predictors. Regression requires metric variables but special techniques are available for using categorical variables as well. Multiple Regression – Example I run a […]
SPSS Regression Basics Simple Linear Regression – Quick Introduction SPSS Multiple Regression Analysis – Tutorial Linear Regression in SPSS – A Simple Example Read SPSS Stepwise Regression Stepwise Regression in SPSS – Data Preparation Read Stepwise Regression in SPSS – Example Stepwise Regression in SPSS – Example 2 Regression – Dummy Variables Creating Dummy Variables […]
A car brand had 18 respondents rate 3 different car ads on attractiveness. The resulting data -part of which are shown above- are in adratings.sav. Some background variables were measured as well, including the respondent’s gender. The question we’ll try to answer is:are the 3 ads rated equally attractive and does gender play any role here?Since […]
What is Repeated Measures ANOVA? Repeated Measures ANOVA Assumptions Quick Data Check Running Repeated Measures ANOVA in SPSS Interpreting the Output Reporting Repeated Measures ANOVA 1. What is Repeated Measures ANOVA? SPSS repeated measures ANOVA tests if the means of 3 or more metric variables are all equal in some population. If this is true and we inspect a sample from our […]
Null Hypothesis Assumptions Example Repeated Measures ANOVA – Basic Formulas Post Hoc Tests Null Hypothesis The null hypothesis for a repeated measures ANOVA is that3(+) metric variables have identical means in some population. The variables are measured on the same subjects so we’re looking for within-subjects effects(differences among means). This basic idea is also referred to as dependent, […]
For testing if 3 or more variables have identical population means, our first option is a repeated measures ANOVA. This requires our data to meet some assumptions -like normally distributed variables. If such assumptions aren’t met, then our second option is the Friedman test: a nonparametric alternative for a repeated-measures ANOVA. Strictly, the Friedman test can […]
SPSS Cochran Q test is a procedure for testing if the proportions of 3 or more dichotomous variables are equal in some population. These outcome variables have been measured on the same people or other statistical units. SPSS Cochran Q Test Example The principal of some university wants to know whether three examns are equally difficult. Fifteen […]
SPSS paired samples t-test is a procedure for testing whether the means of two metric variables are equal in some population. Both variables have been measured on the same cases. Although “paired samples” suggests that multiple samples are involved, there’s really only one sample and two variables. The screenshot below illustrates the basic idea. SPSS […]
The sign test for two medians evaluates if 2 variables measured on 1 group of cases are likely to have equal population medians.* It can be used on either metric variables or ordinal variables. For comparing means rather than medians, the paired samples t-test and Wilcoxon signed-ranks test are better options. Adratings Data We’ll use adratings.sav throughout this tutorial. It holds data on 18 respondents […]
For comparing two metric variables measured on one group of cases, our first choice is the paired-samples t-test. This requires the difference scores to be normally distributed in our population. If this assumption isn’t met, we can use Wilcoxon S-R test instead. It can also be used on ordinal variables -although ties may be a real issue for Likert items. […]
SPSS McNemar test is a procedure for testing if the proportions of two dichotomous variables are equal in some population. The two variables have been measured on the same cases. SPSS McNemar Test Example A marketeer wants to know whether two products are equally appealing. He asks 20 participants to try out both products and […]
A hospital wants to know how a homeopathic medicine for depression performs in comparison to alternatives. They administered 4 treatments to 100 patients for 2 weeks and then measured their depression levels. The data, part of which are shown above, are in depression.sav. Data Inspection – Split Histogram Before running any statistical tests, let’s first just […]
SPSS One-Way ANOVA tests if the means on a metric variable for three or more populations are all equal. * The populations are identified in the sample by a categorical variable. For a very simple explanation of the basic idea, see ANOVA – What Is It?. SPSS One-Way ANOVA Example A farmer wants to know if the weight of parsley plants is […]
ANOVA -short for “analysis of variance”- is a statistical technique for testing if 3(+) population means are all equal. ANOVA – Null Hypothesis Test Statistic – F Assumptions for ANOVA Effect Size – (Partial) Eta Squared ANOVA – Post Hoc Tests The basic idea behind ANOVA: are 3(+) population means all equal? The two simplest […]
Research Question How to lose weight effectively? Do diets really work and what about exercise? In order to find out, 180 participants were assigned to one of 3 diets and one of 3 exercise levels. After two months, participants were asked how many kilos they had lost. These data -partly shown above- are in weightloss.sav. We’re […]
In ANOVA, we always report the F-value, degrees of freedom (df) and p for each effect -possibly just one for one-way ANOVA. P (“Sig.” in SPSS) tells us the likelihood of some effect being zero in our population. However, it doesn’t tell us how strong some effect is if it is not zero; we can’t conclude that p = 0.05 indicates a […]
