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STAT 110 - Section 5 Lecture 13

STAT 110 - Section 5 Lecture 13. Professor Hao Wang University of South Carolina Spring 2012. TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: A A A A A. Last time. Categorical and quantitative variables

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STAT 110 - Section 5 Lecture 13

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  1. STAT 110 - Section 5 Lecture 13 Professor Hao Wang University of South Carolina Spring 2012 TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: AAAAA

  2. Last time • Categorical and quantitative variables • The DISTRIBUTION of a variable tells us what values it takes and how often it takes these values. A distribution can be described by a table, graph, list, or function

  3. Last time

  4. Chapter 11 – Displaying Distributions with Graphs Histograms are the most common graph used to display the distribution of a quantitative variable.

  5. How to Make a Histogram • Divide the range of the data into classes of equal width. • Count the number of individuals in each class. • Draw the histogram.

  6. Histograms • Example • Let’s consider test scores.88, 90, 62, 76, 84, 89, 92, 73, 55, 76, 88, 47, 77, 93 • What’s the range? • So, how should we divide the range into classes? • How many of the scores belong in each class? • Draw the histogram.

  7. Histograms 88, 90, 62, 76, 84, 89, 92, 73, 55, 76, 88, 47, 77, 93

  8. Histograms • You must use your judgment in choosing classes to display the shape of the data. • Too few classes will give a “skyscraper” effect, with all values in a few classes with tall bars. • Too many classes will give a “pancake” effect, with most classes having one or no observation. • The left endpoints of the bars are included, the right aren’t.

  9. A Sample Data Set

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