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38 Chapter 1 %u2022 Analyzing One-Variable Data Here are a few tips to consider when making a stemplot: %u2022 There is no magic number of stems to use. Too few or too many stems will make it difficult to see the distribution%u2019s shape. Five stems is a good minimum. %u2022 If you split stems, make sure that each stem is assigned an equal number of possible leaf digits. That is, split each stem into 2 stems with 5 possible leaves each, or into 5 stems with 2 possible leaves each. %u2022 When the data have too many digits, you can get more flexibility by rounding or truncating the data. Making a Stemplot You can use technology to make a stemplot. We%u2019ll illustrate using the electoral vote data from the preceding example. Applet 1. Go to stapplet.com and launch the One Quantitative Variable, Single Group applet. 2. Enter %u201cElectoral votes%u201d as the Variable name. 3. Select Raw data as the input method. 4. Type the data values separated by spaces or commas, or copy-and-paste them from a file. 5. Click the Begin analysis button. 6. Change the Graph type to a stemplot. 7. Choose the option to split the stems into two groups to get a better picture of the distribution. Graph DistributionGraph type:Split stems:Shift stem additional decimal places to the left, truncating as needed.StemplotNoYes, into two groups0Collapse groups of empty stems?001122334453 3 3 3 3 3 3 4 4 4 4 4 4 45 5 6 6 6 6 6 6 7 7 8 8 8 9 90 0 0 0 0 1 1 1 1 2 3 45 6 6 7 9 98004 Electoral votesKEY: 5|4 = 54TECHCORNER Describing Stemplots Making a stemplot is just the beginning. We also need to describe what we see. Consider the stemplot of caffeine content (in milligrams per 8-ounce serving) in popular soft drinks. It is roughly symmetric with two distinct peaks: one in the 25 to 29 mg stem and one in the 35 to 39 mg stem. The data values vary from 15 to 47 mg of caffeine per 8-ounce serving. Here%u2019s an interesting comparison: some energy drinks have more than 70 mg of caffeine per 8-ounce serving! 1 5562 0333442 556677788888993 1133 555677784 334 77KEY: 2 | 8 means thesoft drink contains28 mg of caffeine per8-ounce serving.%u00a9 Bedford, Freeman & Worth Publishers. For review purposes only. Do not distribute.