Final answer:
The described sampling method, where every 15th phone number on every 5th page of the phone book is called, is categorized as Systematic Sampling.
Step-by-step explanation:
The instruction to call every 15th phone number on every 5th page of the phone book describes Systematic Sampling. This method involves selecting a sample from the population through a systematic process, such as choosing every nth individual. In this case, the 'nth' term corresponds to the 15th phone number on the 5th page. It is not random because it follows a predetermined pattern, nor is it stratified because it does not involve dividing the population into subgroups before sampling. It is also not convenience sampling since it does not involve choosing individuals who are conveniently available.