Write a commentary on the validity of the findings reported in the Arif et al. s

Write a commentary on the validity of the findings reported in the Arif et al. study. Use the following questions to guide your response:
What are the strengths of the study in terms of internal validity (credibility), that is, the extent to which the interpretation of the findings is credible, based on the design and the data? What are some possible weaknesses?
What are the strengths of the study in terms of external validity(generalizability/transportability), that is, the extent to which the findings could generalize beyond this particular iteration of the design? What are some possible limitations?
All sources must be appropriately referenced. 
Recommended length: 500 words.