1. Visual Displays for Quantitative Data
each response is a numerical value
Dot plot….
Stemplot……………………….
Histogram………………………………..

2. Stemplot (also called a stem and leaf plot)
Will show the distribution of the data while including the actual numerical values
5 | 2 = 52
12 | 5 = 125
0 | 8 = 8
Stem Leaf
Include a title (with units/context)
Make a column of the stems from lowest to highest
Include stems that have no leaves
Record the leaves next to their matching stem (IN ORDER)
Include a vertical line between the stem and its leaves
Provide a key to explain how the values are represented

3. Let’s Try one:

4. What are some drawbacks of stemplots??
You can also use a stemplot to compare multiple sets of data. These are called back to back stemplots.
What are some drawbacks of stemplots??
Stemplots do not work well with large sets of data
Splitting stems can sometimes give a better view of the
distribution (Each stem appears twice, leaves 0 – 4 on first line,
5 – 9 on second…this can also be done into 5 stems)
Trimming can also be used when numbers are very larger ($34,567 can be rounded to $35,000 and then only 35 can be used with the key indicating units are in thousands)

5. The goal when critically looking at a graph is to look for patterns and unique situations that differ from the general pattern in the graph. This can include (but not limited to):
Outliers – extreme values that are higher or lower than the rest of the data group
Clusters – separate groupings within the data
Gaps – space between data where no values occur

6. Histograms
Graph that displays a frequency distribution and each bar shows the count (frequency) or percent of that class
Classes must be of equal width when created
Bars therefore must also be of equal width
Use your judgment with the number of classes used… 5 – 10 is usually a good rule…software programs will do this for you

7. DESCRIBING THE DISTRIBUTION
Describe the shape of the distribution
Symmetric Skewed Left Skewed Right
2) Describe the center of the distribution (use mean or median)
3) Describe the spread of the distribution (range, SD, or IQR)
Identify any POSSIBLE or APPARENT outliers as well as any gaps or clusters

8. Creating Histograms and Describing the Distribution
Enter Data into a calculator list, L1.
Press 2nd Y= (Stat Plot)
Press enter to go to Plot 1
Adjust setting to create a histogram
Press the ZOOM button, then press 9 (Stat Zoom)