Statistical Concepts in Research Design

A researcher is interested in studying the effects of sleep on memory retention. She decides to conduct an experiment where she compares two groups: one group that sleeps for 8 hours and another group that sleeps for only 4 hours on the same night. Afterward, both groups take a memory test to assess their retention of information learned the day before.

Identify and explain the two statistical concepts that are most important to understand in analyzing the collected data from this experiment. Be sure to define each concept clearly and describe how it is relevant to the research design.