The Chi-square goodness-of-fit test is a statistical method used to determine if a sample data set matches a population with a specific distribution. It compares the observed frequencies of outcomes in the sample to the expected frequencies based on a hypothesized distribution. If the differences between these frequencies are significant, it suggests that the sample does not fit the expected distribution. This test is commonly applied in various fields, such as biology, social sciences, and market research, to assess categorical data. It helps researchers understand whether their data aligns with theoretical expectations or if there are notable deviations that warrant further investigation.