There are several statistical tests that can be used to investigate correlations between variables based on the type of data and study design:
- A z-test can compare a sample proportion to a population proportion to see if they are significantly different, as when comparing PKU rates.
- Spearman's rank correlation or Pearson's correlation can measure the strength and direction of relationships between ordinal or interval/ratio variables.
- A t-test can analyze differences between repeated measures before and after an intervention to see if they are statistically significant.
- A chi-square test can determine if there is a relationship between categorical variables, such as student responses on a Likert scale. The appropriate test depends on the data