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When designing an experiment in statistics, it's crucial to ensure that the structure allows for a clear comparison of results. It benefits such an experiment to include a control group—in this case, the recall scores without imagery—and a test group, which received imagery instructions. This setup permits the evaluation of the imagery effect on memory recall by comparing outcomes from the two conditions.

Crucial to this design is the concept of random assignment, ensuring that each participant has an equal chance of being included in either group to limit the influence of external factors. Furthermore, consistency in delivering instructions and measuring outcomes across all participants is crucial to minimize variability that isn’t related to the independent variable being tested—in our example, the presence or absence of imagery instructions. By maintaining strict protocols, experimenters can attribute differences in recall scores to the imagery instructions with greater confidence.

Calculating average scores is a fundamental statistical procedure to summarize a set of data. The average, also known as the mean, is the sum of all the values divided by the number of values. In the context of our recall experiment, we calculate the average recall score with imagery and without imagery separately.

To make these calculations, sum up all the individual scores in each condition, and then divide that sum by the total number of observations (or students, in this case). The resulting figures—the average scores—represent a central tendency of the group's performance under each experimental condition. These averages allow us to make a direct comparison between the two conditions to answer the research question: does using imagery improve memory recall?

The 'imagery effect' refers to the phenomenon where the creation of mental images can aid in the process of memory recall. Cognitive psychology suggests that adding a visual representation to verbal information can make the material more concrete and, therefore, easier to retrieve later.

In the experiment at hand, the comparison of recall scores with and without the use of imagery provides empirical data to test the effect of imagery on memory. If the average recall score for the imagery group is higher than that of the non-imagery group, it would suggest that forming mental images can play a positive role in enhancing memory recall. This effect may relate to the dual-coding theory, which posits that humans process visual and verbal information in separate channels in the brain, and combining them enhances memory.