Final answer:
Consumer assertion, defined as the total number of products returned in one year, is a measure of frequency, which is the number of times an event occurs in statistics.
Step-by-step explanation:
The experimenter's definition of consumer assertion as the total number of products that a consumer has returned for his or her money back in one year is a measure of D) frequency. This is because frequency refers to the number of times an event occurs. In the context of statistics, the other options provided (mean, median, standard deviation) are measures of central tendency and dispersion, not the count of occurrences.
To illustrate using a provided example, the grocery store study calculates the average (or mean) spending per visit in the sample of 1,000 visits, which is a statistic. The frequency would be if they counted how many times a specific amount was spent, such as how many times customers spent exactly $15.