<u>Loss to follow-up: </u>In psychological research, the term "loss-to-follow-up" is described as a process that occurs when an experimenter or researcher lose his or her contact with the participants in a specific trial for reasons like migration or in fact the failure to maintain some contact prior to the termination or end of a research or study or of any planned endpoints.
<u>It often leads to create bias</u> while researching through observational method as the observation depends on the researcher itself.
The type of sampling used in the example is 'stratified sampling'.
<u>Explanation:
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The term 'stratified' used to name the method of sampling is referred to as 'fixed' or definite.
If we keenly process the data that is given in the example, we can find that the number of students chosen for the study from each category makes up 10 percent of the entire category.
As the researcher has chosen to carry out the study with a definite 10 percent of students from each category, the sampling method can be concluded to be 'stratified sampling'.
