# Displaying Data

###### Engineering Statistics - STAT3115 - 23 January 2018

### Stem-and-Leaf Displays

- For numerical data (not categories)
- Original data can be recovered
- Instructions:
- Select one or more leading digits for the stem values (5-20 stems is recommended)
- Remaining digits are the leaves
- List the possible stem values (in decreasing order) in a vertical column
- Draw a vertical lie to the the right

- Data received from Stem-and-Leaf:
- Typical or representative Value
- Spread about the typical value
- Gaps
- Symmetry
- symmetric
- bimodal
- right (positively) skewed
- left (negatively) skewed

- Number of locations or peaks
- Presence of outlying data

### Dotplots

- Good for small data sets or when there are few distinct values (lots of repeats)
- Better to use histograms for larger data sets

### Histograms

A bar plot

- Each data value can be:
- Numerical or Quantitative
- Categorial or Qualitative