Here's what Minitab's stem-and-leaf plot of the 64 IQs looks like: Stem-and-Leaf of IQ Instead, you'd probably want to let some statistical software, such as Minitab or SAS, do the work for you. First and foremost, no one in their right mind is going to want to create too many of these stem-and-leaf plots by hand. That's all well and good, but we could do better. the smallest IQ in the data set is 68, while the largest is 141.most of the IQs are in the 90s and 100s.Now, rather than looking at a list of 64 unordered IQs, we have a nice picture of the data that quite readily tells us that: Here's what the our stem-and-leaf plot would look like after adding the first five numbers 111, 85, 83, 98, and 107:Īnd here's what the completed stem-and-leaf plot would look like after adding all 64 leaves to the nine stems: Once the column of stems are written down, we work our way through each number in the data set, and write its leaf in the row headed by its stem. To create the plot then, we first create a column of numbers containing the ordered stems. We could divide 83 into a stem of 8 and a leaf of 3. We could divide 85 into a stem of 8 and a leaf of 5. We could divide our first data point, 111, for example, into a stem of 11 and a leaf of 1. The basic idea behind a stem-and-leaf plot is to divide each data point into a stem and a leaf. A stem-and-leaf plot, on the other hand, summarizes the data and preserves the data at the same time. ![]() One primary disadvantage of using a histogram to summarize data is that the original data aren't preserved in the graph. We could, of course, summarize the data using a histogram. ![]() Once the data are obtained, it might be nice to summarize the data. After each person completed the test, they were assigned an intelligence quotient (IQ) based on their performance on the test. Create a side-by-side stem-and-leaf plot of these wins and losses.A random sample of 64 people were selected to take the Stanford-Binet Intelligence Test. The table shows the number of wins and losses the Atlanta Hawks have had in 42 seasons. Presidential Ages at Inauguration: President Construct a side-by-side stem-and-leaf plot using this data. The two following tables show the ages of presidents at their inauguration and at their death. ![]() The leaves are to the left and the right of the stems. In a side-by-side stem-and-leaf plot, two sets of leaves share the same stem. ![]() It takes some background information to explain outliers, so we will cover them in more detail later.Ī side-by-side stem-and-leaf plot allows a comparison of the two data sets in two columns. Some outliers are due to mistakes (for example, writing down 50 instead of 500) while others may indicate that something unusual is happening. When you graph an outlier, it will appear not to fit the pattern of the graph. An outlier is an observation of data that does not fit the rest of the data. You want to look for an overall pattern and any outliers. The stemplot is a quick way to graph data and gives an exact picture of the data. Eight out of the 31 scores or approximately 26% (\frac) were in the 90s or 100, a fairly high number of As.Ģ 2 3 4 8Ġ 2 2 3 4 6 7 7 8 8 8 9Ġ 0 1 2 2 2 3 4 6 7 7 The stemplot shows that most scores fell in the 60s, 70s, 80s, and 90s.
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