In a statistical study, what does the sample size refer to?

The sample size in a statistical study is defined as the total number of observations in the sample. It quantifies the number of individual data points or units collected from a larger population for analysis. A larger sample size typically lends more credibility to the results of a study, as it can reduce the margin of error and increase the reliability of the findings. In essence, it helps in better estimating the characteristics of the whole population from which the sample is drawn.

The other options do not accurately define sample size. The average response pertains to a specific statistic calculated from the sample data, the level of measurement refers to the way data is categorized or quantified, and the proportion of the population studied relates to how much of the population is represented by the sample, which is not the same as the sample size itself. Thus, recognizing that the sample size is strictly about the count of observations ensures a clearer understanding of its importance in statistical studies.