lecture+2 - January 11, 2008 [LECTURE 2] What you need to...

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[ LECTURE 2 ] 1 What you need to remember for today’s class I. Histograms: The range of values that a variable can take is divided into equal-size intervals. The histogram shows the number of individual data points that fall in each interval. Example: The first column represents all states with a percent Hispanic in their population between 0% and 4.99%. The height of the column shows how many states (27) have a percent Hispanic in this range. The last column represents all states with a percent Hispanic between 40% and 44.99%. There is only one such state: New Mexico, at 42.1% Hispanic II. Important: How to create a histogram It is an iterative process— try and try again. What bin size should you use? Not too many bins with either 0 or 1 counts Not overly summarized that you lose all the information Not so detailed that it is no longer summary Rule of thumb : Start with 5 to10 bins. Look at the distribution and refine your bins. (There isn’t a unique or “perfect” solution.)
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lecture+2 - January 11, 2008 [LECTURE 2] What you need to...

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