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# Exploring data stemplot

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### Exploring data stemplot

1. 1. Exploring Data Describing Distributions Graphically
2. 2. Graphs for Categorical Variables • Pie Charts • Include all categories that make up a whole • Use software to help make these *round-off error may cause pie charts not to add up to 100% • Bar Graphs • Display a distribution of a categorical variable • Compares any set of quantities that are measured in the same units • Leave spaces between the bars
3. 3. Stemplots (aka stem and leaf plots) • Let’s you see the shape of the distribution How do you make a stemplot? 1. Separate data into stem (all values to the left of the leaf) and leaf (only 1 digit) 2. Write all stems from smallest to largest in a vertical column Draw a vertical line to the right of the stems 3. Write each leaf in the appropriate stem row. Make sure they go from increasing order from the stem outward 4. Key/labels – be sure to give a key to interpret the stemplot as well as label it appropriately. Example Key: 453.34 = 453.3|4
4. 4. Back to Back Stemplots Use a back to back stemplot to compare the shapes of 2 distributions such as male vs. female Put the stem in the middle of the plot Place leaves going outward from the stem Note: Stemplots don’t work well when you have a lot of data with spread out stems or where each stem must contain a large number of leaves
5. 5. Modifying Stemplots • Splitting Stems • Use a split when you have a large number of leaves for a particular stem. 1st stem would have leaves 0-4, 2nd stem would have leaves 5-9 Trim a stem plot by removing the last digit if observed values have many digits that would make the creation of the stemplot meaningless