Final answer:
The 3rd type of psychological research that includes Correlational and Descriptive is observational research. Observational research is a type of nonexperimental scientific investigation in which the researcher measures characteristics in a sample but does not attempt to manipulate or control variables of interest.
Step-by-step explanation:
The 3rd type of psychological research that includes Correlational and Descriptive is observational research. Observational research is a type of nonexperimental scientific investigation in which the researcher measures characteristics in a sample but does not attempt to manipulate or control variables of interest. This type of research allows researchers to observe and describe behaviors or phenomena in their natural settings.