平均絶対偏差

Mean absolute deviation is calculated by finding the average distance of data values from the mean. First, compute the sample mean. Then calculate the deviation for each value by subtracting the mean. Take absolute values of these deviations, sum them, and divide by the sample size. For example, with cupcake data of 10, 15, 8, 7, and 10, the mean is 10, absolute deviations sum to 10, yielding a mean absolute deviation of 2.

Absolute values are used because positive and negative deviations cancel each other out when added together, resulting in zero. This zero value is unhelpful for measuring variability. By taking absolute values of all deviations before summing, we obtain a meaningful non-zero measure that accurately reflects the average distance of data points from the mean.

Mean absolute deviation uses a non-algebraic modulus operation to calculate variability, while calculating standard deviation uses algebraic operations. Because mean absolute deviation employs non-algebraic methods, it cannot be used in inferential statistics, which requires algebraic operations. Standard deviation is therefore preferred for statistical inference.

No, mean absolute deviation is not suitable for inferential statistics because it involves a non-algebraic modulus operation, while inferential statistics requires algebraic operations. Additionally, mean absolute deviation is a biased statistic—the calculated mean absolute deviation of a sample does not adequately represent the population mean absolute deviation.

A biased statistic means the sample estimate does not accurately represent the population parameter. For mean absolute deviation, the value calculated from a sample does not adequately represent the true mean absolute deviation of the entire population. This bias limits its reliability for making population-level inferences or generalizations.

Mean absolute deviation measures variability by quantifying the average distance of data points from the mean. It reflects how spread out values are in a dataset. A larger mean absolute deviation indicates greater variability, while a smaller value indicates data points cluster closer to the mean.

Mean absolute deviation has two primary limitations: it cannot be used in inferential statistics due to its non-algebraic nature, and it is a biased statistic that does not reliably represent population parameters. These constraints make it less suitable than other measures for advanced statistical applications.