Answer:
a. Describing a sample with mean and standard deviation.
Step-by-step explanation:
Statistics can be categorized into descriptive and inferential statistics.
descriptive statistics uses data for descriptions through numerical analysis. It can be further divided in four parts.
Inferential statistics however is based on assumptions and conclusions and generalizations drawn from samples or checks.
options b to d are all examples of inferential statistics while option a is an example of descriptive statistics.