Statistical Sampling

There are 600 Sephora locations in the United States. Christine randomly selected 40 stores, and then she randomly selected 100 customers from each of those stores. Less than 1% of her sample identified as heterosexual males. Based on her sample, the average spending at Sephora is $45. In addition, 340 customers in her sample revealed that they have VIB Rouge status, which the highest tier status that is reached when a customer spends $1,000 in a calendar year.

What was Christine’s sampling method?
More Statistical Sampling Questions: