Final answer:
When pairs tested did not show a change in weight, it suggests the change was within the just-noticeable difference which is not reliably detected due to human sensory limitations.
Differences in weight perception are expected to vary depending on whether the base weight is 1 or 20 pounds. Repeated experiments will average out results, but some variation is always expected.
Step-by-step explanation:
In the context of testing the just-noticeable difference (JND) in weights, if pairs tested did not have a change in weight, this could be due to the limits of human perception at certain scales. According to the principles discovered by Weber and Fechner, the difference threshold is the minimum difference between two stimuli that a person can detect, which is proportional to the magnitude of the stimuli. Therefore, participants may not notice a weight change if it is within this threshold.
When all participants found a specific step weight to be equal with a one-pound base weight, it's likely that the increment was within the JND for one pound. For the 20-pound group, the JND would be higher since it is based on a percentage of the base weight, making smaller increments harder to detect.
Repeated experiments may yield different results due to variations in individual sensitivity and other variables, but generally, a large number of trials can produce more consistent results as they average out anomalies. However, variability in human perception will likely mean that not all experiments will yield identical outcomes.