Question

where do correlational designs fall in terms of internal, external, and construct validity in a research study?

Answer 1

Any experimental research tries to establish a relation between Independent variable (IV) and Dependent Variable (DV).
External validity measures how the results stands true when compared to real world.
internal validity is the measure of how accurate is the cause effect between IV and DV and is usually measured by looking at confounding variables , that may cause change in DV besides the IV.
Construct validity measure - to what extent the experiment meauseres what it intends to measure.

In correlation studies, there are no control or manipulation of IV, and there may be high confounding variables . so there will be very less internal validity. However, since they are not manipulated or controled , their findings matches to the real world observation , therefore have high external validity.
As far as construct validity is considered, it is not much relevant for correlational studies. Since there are large confounding variables so it cannot be accurately predicted whether scorrelational study measures what it intends to measure or not.