IBM Data Science Practice Test

Which measure is not affected by extreme values in a dataset?

1. Mean

2. Median

3. Variance

4. Standard deviation

The correct answer is: Median

The median is the correct answer because it is a measure of central tendency that represents the middle value in a sorted dataset. When data points are arranged in order, the median is simply the value that separates the higher half from the lower half. This characteristic makes it robust to extreme values, or outliers, since these outliers do not impact the position of the middle value. For instance, in a dataset such as {1, 2, 2, 3, 100}, the median remains 2, despite the presence of the extreme value 100. This stability under the influence of extreme values differentiates the median from the mean, which can be skewed significantly by outliers, and from variance and standard deviation, which both measure how data points spread around the mean, thus being heavily influenced by extreme values.