The median is closer to the third quartile than to the first quartile. Skewness suggests that data may not be normally distributed.

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Histograms and box plots can be quite useful in suggesting the shape of a probability distribution.

Skewed left box plot. Look for signs of skewness. Look for potential outliers see above image. The mean is typically less than the median.

Normal distribution or symmetric distribution. When a box plot is left skewed values gather at the upper end making a short and tight section there. Compare the medians of box plots.

To the left of that crowd data points spread out creating a longer tail. Here we ll concern ourselves with three possible shapes. Box plots are useful as they show outliers within a data set.

Skewed data show a lopsided boxplot where the median cuts the box into two unequal pieces. If the longer part of the box is to the right or above the median the data is said to be skewed right. A distribution that is skewed left has exactly the opposite characteristics of one that is skewed right.

For a distribution that is positively skewed the box plot will show the median closer to the lower or bottom quartile. Box plots are like the base of distribution curves. The box plot will look as if the box was shifted to the left so that the right tail will be longer and the median will be closer to the left line of the box in the box plot.

A boxplot can show whether a data set is symmetric roughly the same on each side when cut down the middle or skewed lopsided. If the distribution is skewed to the left most values are large but there are a few exceptionally small ones. Compare the interquartile ranges and whiskers of box plots.

The boxplot with right skewed data shows wait times. A symmetric data set shows the median roughly in the middle of the box. If the longer part of the box is to the right or above the median the data is said to be skewed right.

A few items fail immediately and many more items. The tail of the distribution is longer on the left hand side than on the right hand side. Skewness indicates that the data may not be normally distributed.

For a distribution that is skewed left the bulk of the data values including the median lie to the right of the mean. Most of the wait times are relatively short and only a few wait times are long. If the longer part is to the left or below the median the data is skewed left.

The following boxplots are skewed. The boxplot with left skewed data shows failure time data. If a box plot has equal proportions around the median we can say distribution is symmetric or normal.

Symmetric skewed left or skewed right.