What is the process for ensuring an adequate and proper sample size for a study?  What are disadvantages of a convenience sample? What are three disadvantages to an observa

Post your answer to 1 of the 3 questions with explanation and details. Please follow the Community Café Guidelines for participating in the Community Café. 

1. What is the process for ensuring an adequate and proper sample size for a study? 
2. What are disadvantages of a convenience sample?
3. What are three disadvantages to an observational study design?