Final answer:
Without specific information about sampling methods and constraints, it's impossible to determine the number of cases of samples from 40 patients. Convenience sampling with familiar patients introduces bias, and sample size adequacy varies with context. The answer is option 1.
Step-by-step explanation:
To determine how many cases of samples can be obtained from 40 patients, we need more information. For instance, how many samples are taken from each patient, and are there any constraints on the sampling process? Without additional details, we can't make an accurate claim, so the answer is Cannot be determined.
If a researcher were to select 40 patients they knew for a survey, this would be considered convenience sampling, which is not a random sampling method. This approach could introduce bias into the data set, as the patients may not accurately represent the broader population.
When considering the validity of a sample size related to a larger population, it depends on the context. For instance, a sample size of 150 might be sufficient for studying a single school's population, but a sample size of two would not be representative of a population of five. Such decisions regarding sample size and sampling methods directly impact the reliability of data and the conclusions drawn from it.