Final answer:
Use the mean and MAD for symmetric distributions, and the median and IQR for skewed distributions; skewness affects the mean, making the median a better central tendency measure for skewed data.
Step-by-step explanation:
When comparing two populations, the choice between using the mean and the mean absolute deviation (MAD), or the median and the interquartile range (IQR), depends on the shape of the distributions. For symmetric distributions where the data values are evenly spread around the center, the mean and MAD are appropriate. This is because the mean is an accurate measure of central tendency when each side of the distribution is a mirror image of the other, and the MAD provides a measure of variability that is not affected by extreme values.
However, when distributions are skewed (either positively or negatively), the median and IQR are preferred. Skewness causes the mean to be pulled in the direction of the tail, which may not represent the center of the data accurately. In such cases, the median is a better measure of central tendency because it is less affected by extreme values. Similarly, the IQR, which measures the range between the first and third quartiles, provides a clearer picture of the spread of the middle 50 percent of the data without being influenced by outliers.