Simple Quantitative Displays
Key Questions

A normal distribution is completely symmetrical, a skew distribution is not.
In a positively skewed distribution, the "toe" at the larger side is longer than at the other side, causing the median, and especially the mean, to move to the right. In a negatively skewed distribution these move to the left, because of a longer "toe" at the smaller values.
While in a nonskewed normal distribution mode, median and mean are all at the same value.
(pictures from internet)

Dotplots and stemplots are suitable for the visual representation of numerical ( quantitative) data, in particular for small to mediumsized data sets .
For categorical (qualitative) data, the bar chart is the preferable way of visual representation.