The type of sample that was used by this manager is: systematic sampling.
Sampling can be defined as a process that is used by researchers to collect or select data such as objects, observations, or individuals from a larger statistical population, especially through the use of specific procedures.
In Statistics, there are different types of sampling used by researchers and these include the following;
A systematic sampling refers to a type of probability sampling method that involves a researcher collecting or selecting data from a larger population, especially by selecting an ordered (fixed) sample population at periodic interval such as the 20th pizza.
Read more on systematic sampling here: https://brainly.com/question/18957000