Answer:
Quota.
Step-by-step explanation:
In Statistics, sampling can be defined as a process used to collect or select data (objects, observations, or individuals) from a larger statistical population using specific procedures.
There are various types of sampling used by researchers and these are;
1. Random sampling.
2. Systematic sampling.
3. Stratified sampling.
4. Cluster sampling.
5. Opportunity or convenience sampling.
6. Quota sampling.
Quota sampling can be defined as a non-probability sampling technique wherein a sample comprising of data from a population or homogeneous group are created.
In this scenario, a researcher selects a sample from a district such that 25% of the children are between ages 5 and 6, 25% are between ages 7 and 8, 25% are between 9 and 10, and 25% are between ages 11 and 12. Thus, the researcher is employing a quota sampling.