The chi-square (χ2) is a nonparametric statistical test used for data analysis when one or more variables are nominal or categorical in nature. The test determines if the differences observed among variable categories are due to chance or if they are statistically significant. It can be used with single or multiple samples and is a nonparametric test, which means that it is not based on the probabilistic distribution of the normal curve.
Nonparametric tests are used when the data being analyzed are from the nominal or ordinal scale of measurement or when data collected at [Page 129]the interval or ratio level violate assumptions of normality. In such cases the data are transformed from the interval or ratio level into ordinal or nominal levels ...
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