7. the median is better than the mean because it isn't influenced by extremely large values. it is generally better to use the median as opposed to the mean for a simple reason: the mean or average is very sensitive to outliers (abnormally low or high values), while the median is much less affected by outliers.
8.
A median chart is a special-purpose variation of the X-bar chart. This chart uses the median instead of the subgroup average to show the system's central location. The median is the middle point when data points are arranged from high to low. The chart shows all the individual readings.
