Difference between two examples of sampling

This post is in responce to your activity on the difference between the two samplings.
http://metca6research.blogspot.com/

According to me the differences are;
The reseracher in the first example is selecting samples randomly from the entire Mumbai city, that is by simple random sampling. So the findings those she will come up with will be generlised to population of the city.
Whereas the researcher in the second example is selecting her own batch as her sample, that is by convenience sampling. But in the class she is selecting samples randomly for the two CAI packages, that is by simple random sampling. So her results will be generaliable only to her batch.