Final answer:
The sampling technique described is stratified sampling, which involves dividing the population into strata and taking random samples from each stratum.
Step-by-step explanation:
The sampling technique used to obtain a sample where a group of people are classified according to income and then random samples of people from each group are taken is known as stratified sampling. This method involves dividing the population into subgroups, known as strata, based on a specific characteristic, such as income in this case. Then, a random sample from each stratum is selected.