Final answer:
Mildred is performing a correlational study to determine the association between income and personality traits, which reveals relationships but doesn't establish causality.
Step-by-step explanation:
Mildred is conducting a type of study known as correlational research. This kind of study examines whether an association or relationship exists between two variables—in this case, income and personality traits. It is important to note that while correlational studies can identify relationships between variables, they do not establish causal connections. To determine causality, an experimental study would be necessary, where the researcher manipulates one variable to see the effect on another. Nevertheless, correlational research can provide valuable insights into trends and associations that may merit further investigation.