T Test, Chi-Square Test, Correlation, ANOVA, Regression, Nonparametric Tests,
The Kruskal-Wallis test is an alternative for a one-way ANOVA if the assumptions of the latter are violated. We’ll show in a minute why that’s the case with creatine.sav, the data we’ll use in this tutorial. But let’s first take a quick look at what’s in the data anyway. Quick Data Description Our data contain the result of a small […]
Null Hypothesis Assumptions Levene’s test in SPSS Output Reporting Levene’s Test – What Is It? If we want to compare 3(+) groups on a metric variable, we usually want to know if they have different mean scores. In most cases, we’ll run an ANOVA in order to find out. However, this requires the homogeneity assumption which states that the population […]
The median test for independent medians tests if two or more populations have equal medians on some variable. That is, we’re comparing 2(+) groups of cases on 1 variable at a time. Rating Car Commercials We’ll demonstrate the median test on adratings.sav. This file holds data on 18 respondents who rated 3 different car commercials on […]
The Mann-Whitney test is an alternative for the independent samples t test when the assumptions required by the latter aren’t met by the data. The most common scenario is testing a non normally distributed outcome variable in a small sample (say, n < 25).* The Mann-Whitney test is also known as the Wilcoxon test for independent samples -which shouldn’t be confused […]
Null Hypothesis Assumptions Chi-Square Independence Test in SPSS Output Reporting Null Hypothesis Chi-Square Independence Test A chi-square independence test evaluates if two categorical variables are associated in some population. We’ll therefore try to refute the null hypothesis that two categorical variables are (perfectly) independent in some population.If this is true and we draw a sample from this population, then we […]
If you’d like to know if 2 groups of people score similarly on 1 dichotomous variable, you’ll compare 2 independent proportions. There’s two basic ways to do so: the chi-square independence test and; the z-test for 2 independent proportions. These tests yield identical significance levels but the z-test approach allows you to compute a confidence interval for the difference between […]
SPSS one-sample t-test tests if the mean of a single metric variable is equal to some hypothesized population value. The figure illustrates the basic idea. SPSS One Sample T-Test – Example A scientist from Greenpeace believes that herrings in the North Sea don’t grow as large as they used to. It’s well known that – on average – […]
A sign test for one median is often used instead of a one sample t-test when the latter’s assumptions aren’t met by the data. The most common scenario is analyzing a variable which doesn’t seem normally distributed with few (say n < 30) observations. * This tutorial shows how to run and interpret a sign test in SPSS. We’ll […]
SPSS one-sample chi-square test is used to test whether a single categorical variable follows a hypothesized population distribution. SPSS One-Sample Chi-Square Test Example A marketeer believes that 4 smartphone brands are equally attractive. He asks 43 people which brand they prefer, resulting in brands.sav. If the brands are really equally attractive, each brand should be chosen by roughly […]
The binomial test is the most simple statistical test there is. Understanding how it works shouldn’t be too hard and will help you understand other statistical tests more easily too. So what is it? A binomial test is a procedure for evaluating if some population proportion is x. For example, a marketeer has to make sure that 50% […]
There’s two basic tests for testing a single proportion: the binomial test and the z-test for a single proportion. For larger samples, these tests result in roughly similar significance levels. However, the binomial test only comes up with a 1-tailed p-value unless the hypothesized proportion = 0.5. Moreover, it can’t compute a confidence interval for your proportion. The […]
SPSS binomial test is used for testing whether a proportion from a single dichotomous variable is equal to a presumed population value. The figure illustrates the basic idea. SPSS Binomial Test Example A biologist claims that 75% of a population of spiders consist of female spiders. With a lot of effort he collects 15 spiders, 7 of […]
A dichotomous variable is a variable that contains precisely two distinct values.Let’s first take a look at some examples for illustrating this point. Next, we’ll point out why distinguishing dichotomous from other variables makes it easier to analyze your data and choose the appropriate statistical test. Examples Regarding the data in the screenshot: completed is not a dichotomous variable. It […]
A large bank wants to gain insight into their employees’ job satisfaction. They carried out a survey, the results of which are in bank_clean.sav. The survey included the number of hours people work per week and their gross monthly salaries. Research Question It seems obvious that working hours are related to monthly salaries: employees who work […]
A Pearson correlation is a number between -1 and 1 that indicates the extent to which two variables are linearly related.The Pearson correlation is also known as the “product moment correlation coefficient” (PMCC) or simply “correlation”. Pearson correlations are suitable only for metric variables (which include dichotomous variables). For ordinal variables, use the Spearman correlation or Kendall’s tau and […]
Z-scores are linearly transformed data values having a mean of zero and a standard deviation of 1.Z-scores are also known as standardized scores; they are scores (or data values) that have been given a common standard. This standard is a mean of zero and a standard deviation of 1. Contrary to what many people believe, z-scores are not necessarily […]
Null Hypothesis Assumptions Independent Samples T Test in SPSS Output Reporting Null Hypothesis The null hypothesis for an independent samples t test is that two populations have equal means on some metric variable. For example, do men spend the same amount of money on clothing as women? We can’t reasonably ask the entire population of men and women how much they […]
The variance is a number that indicates how far a set of numbers lie apart.The variance is identical to the squared standard deviation and hence expresses “the same thing” (but more strongly). Variance – Example A study has 100 people perform a simple speed task during 80 trials. For each participant, 80 reaction times (in seconds) are […]
SPSS nonparametric tests are mostly used when assumptions aren’t met for other tests such as ANOVA or t-tests.* Second, nonparametric tests are suitable for ordinal variables too. In rare cases they may have more statistical power than standard tests. Not sure which (nonparametric) test to use? You’ll quickly find the answer in Simple Overview Statistical Comparison Tests. Nonparametric Tests – One Sample SPSS Kolmogorov-Smirnov Test for […]
SPSS Correlation Basics Spearman Rank Correlations – Simple Tutorial SPSS Correlation Analysis Tutorial SPSS CORRELATIONS – Beginners Tutorial Pearson Correlations – Quick Introduction Association Measures Cramér’s V – What and Why? SPSS – Kendall’s Concordance Coefficient W SPSS Scatterplots SPSS Scatterplot Tutorial SPSS – Create All Scatterplots Tool Correlation Tutorials – Other SPSS Confidence Intervals […]
