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Unformatted text preview: Page 1 of 22 January 26, 2009 (3:35pm) J:\SWT\HA4315\Class notes\Spring 2009 version\C_23_Spg 2009.wpd Reduce, reuse, restore, recycle , VOTE Class Twenty Three Agenda & Objectives HA 4315 I. Logistics and Objectives A. Instructor provides evaluation scores for how well the group members graded other group members. B. Memory Jogger II , pp. 66-75, histograms C. Memory Jogger II , pp. 31-35, check sheets I. Memory Jogger II , pp. 66-75, histograms This section reviews earlier material. A histogram is nothing more than a bar chart used to show frequency distributions. A frequency distribution is just a count of how many things fit in each category. Thus, a histogram is just a special kind of vertical bar graph that displays the frequency of data that has been organized into equal intervals. Optimally, these intervals cover all possible values of data so there are no spaces between the bars of the graph. In that case, the horizontal axis is divided into continuous equal intervals. Sometimes there will be outliers at either end that are captured by unequal sized intervals. For example, Bill Gates is worth so much money that to have intervals that went all the way up to his level would end up making a graph that looked very odd. Thus, for “wealth,” you would likely have as the final interval “$10 million net worth or more,” as opposed to equal sized categories that went all the way up to the $55 billion or so that Bill Gates is worth. Manual development of the histogram requires a fair amount of work to get the data ready to graph by organizing it into these ranges and getting a count of how many are in each interval, bin, or range. You can avoid all that work by having Excel do this for you. Tell it the size of the intervals, ranges, or bins (all equivalent terms here). Once this is done, the graph portion is easy. The easiest way to do this in Excel is to bring up the “help” function and type in “histogram.” Excel comes with a “data analysis” package that you have to tell it to load in under “tools.” Once that is installed into the program all you really need to do is specify the bins, intervals, ranges, categories (all equivalent terms here) on the spreadsheet. The bring up the histogram feature and tell it where the data are and where the list of bins is and it will sort them for you. The table below, Figure 2 , from the Groebner & Shannon text, (page 56) presents the raw data and a frequency distribution of salaries for 134 employees in a hypothetical company. We see that forty persons have salaries in the class "$20,000 and under $22,500" and that only six individuals earn $27,500 or more. Note how confusing the salary data are in their raw form when compared to the table below the raw data. Page 2 of 22 January 26, 2009 (3:35pm) J:\SWT\HA4315\Class notes\Spring 2009 version\C_23_Spg 2009.wpd Reduce, reuse, restore, recycle , VOTE Figure 2 Histogram of Salaries 15 20 27 40 19 7 5 5 10 15 20 25 30 35 40 45 1 5 1 7 5 2 2 2 5...
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- Statistics, Histogram, Seven Basic Tools of Quality, \SWT\HA4315\Class notes\Spring