When the sample has been randomly selected, which among the following may be expected in cross-sectional research designs?

A) Strong external validity
B) Weak external validity
C) Weak internal validity
D) Strong internal validity

Choose the most appropriate answer from the options given below.

The correct answer is Only B and C.

Here is the step-by-step educational explanation of why this is the expected outcome in cross-sectional research designs:

1. Understanding Cross-Sectional Design:
A cross-sectional research design is an observational study where researchers collect data from a sample at a single point in time. It provides a "snapshot" of variables but does not track changes over time.

2. Why Internal Validity is Weak (C):
Internal validity measures how confidently a study can establish a causal relationship (that variable X caused variable Y). Because all measurements in a cross-sectional study are taken simultaneously, it is impossible to establish temporal precedence (confirming that the cause occurred before the effect). Due to the inability to rule out alternative explanations or establish cause-and-effect sequences, cross-sectional designs inherently possess weak internal validity.

3. Why External Validity is Weak (B):
External validity is the extent to which the study's findings can be generalized to other populations, settings, or time periods. Although random sampling helps represent the target population at that specific moment, cross-sectional designs are highly susceptible to cohort effects (differences related to the unique historical or cultural experiences of a generation rather than actual development or general truths). Because the data is restricted to a single moment in time, the results cannot be reliably generalized to future time periods or evolving contexts, resulting in weak external validity.

Thus, we can expect both weak external validity and weak internal validity in these designs, making Only B and C the correct answer.