A group of employees at Company A participate in a stress reduction workshop. To evaluate the effectiveness of the workshop, a researcher measures stress levels for these employees before and after the workshop and compares their scores with those from another group of employees at Company B who did not participate in the workshop but were measured at the same two times. What kind of design is being used? a. Mixed design b. Cross-sectional design c. Between-subjects design d. Repeated measures design e. Within-subjects design