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EXPLORING DATA LESSON 1 – 1. Day 2 Displaying Distributions with Graphs Displaying quantitative variables. What are the graphs that are used for organizing quantitative variables and how are they interpreted?. Essential Question:. Objectives :
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EXPLORING DATALESSON 1 – 1 Day 2 Displaying Distributions with Graphs Displaying quantitative variables
What are the graphs that are used for organizing quantitative variables and how are they interpreted? Essential Question: Objectives: • To organize quantitative data into dotplots, stemplots, and histograms.
Warm up # 1 Page 11, problem 1.6 ACCIDENTAL DEATHS • Make a pie chart for the data.
Constructing a Dotplot Step 1: Label your axis and title your graph. Draw a horizontal line and label it with the variable. Step 2: Scale the axis based on the values of the variable. Step 3: Mark a dot above the number on the horizontal axis corresponding to each data value.
Overall Pattern of Distribution To describe the overall pattern of a distribution: • Step 1: Give the center and the spread. (Divide observations in half for now.) • Step 2: See if the distribution has a simple shape that you can describe in a few words. ( State the smallest and largest data.) • Outliers: An outlier in any graph is an individual observation that falls outside the overall pattern.
Constructing a Stemplot Step 1: Separate each observation into a stem consisting of all but the rightmost digit and a leaf, the final digit. Step 2: Write the stems vertically in increasing order from top to bottom, and draw a vertical line to the right of the stem . Go through the data, writing each leaf to the right of its stem and spacing the leaves equally. Step 3: Write the stems again, and rearrange the leaves increasing order out from the stem. Step 4: Title your graph and add a key describing what stems and leaves represent.
Splitting stems • When there are quite a few leaves in a couple of stems, split each stems into two parts. The first will be from 0 to 4 and the second from 5 to 9.
Tips for stemplots • Whenever you split stems, be sure that each stem is assigned an equal number of possible leaf digits. • There is no magic number of stems to use. • Five stems is a good minimum. • You can get more flexibility by rounding the data so that the final digit after rounding is suitable as a leaf. Do this when the data have too many digits.
Constructing a Histogram Step 1: Divide the range of the data into classed of width. Count the number of observations in each class. (each observation should fall in exactly one class.) Step 2: Label and scale your aces and title your graph. Step 3: Draw a bar that represents the count in each class. The base of the bar should cover the class count. *Graphing note:It is common to add a “bread – in – scale “ symbol ( // ) on an axis that does not start at 0.