Are you questioning random samples? Seriously? The notion of representativeness is flawed and often does not work well in practice, i.e. it often leads to biased estimates. Unless there is a good reason for not doing a random sample (mostly for economic considerations), simple random samples are fine.
It's a simple starter example in a blog post. Stratified sampling, with pros and cons, is covered in an intro stats course. This is not an intro stats course, it's a short article on a blog.
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Are you questioning random samples? Seriously? The notion of representativeness is flawed and often does not work well in practice, i.e. it often leads to biased estimates. Unless there is a good reason for not doing a random sample (mostly for economic considerations), simple random samples are fine.
I'm not questioning random sampling. Quite the opposite, and I even said as much in the comment you responded to:
It's a simple starter example in a blog post. Stratified sampling, with pros and cons, is covered in an intro stats course. This is not an intro stats course, it's a short article on a blog.