Class Twenty Four Notes

Class Twenty Four Notes - Page 1 of 16 Class Twenty Four...

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Page 1 of 16 1 Souza, A. D. (July/August 2003) Last word Experience life , p. 92. April 15, 2009 (9:16pm) E:\SWT\HA4315\Class notes\Spring 2009 version\C_24 Spg09.wpd Reduce, reuse, restore, recycle HA 4315 For a long time it seemed to me that life was about to begin–real life. But there was always some obstacle in the way, something to be gotten through first, some unfinished business, time still to be served, or a debt to be paid. Then life would begin. At last it dawned on me that these obstacles were my life. 1 I. Logistics and Objectives A. Normal distribution and the Z tables II. Normal distribution and the Z tables The use of the Z tables allows us to determine the probability of an event happening by chance or if what took place was likely not due to chance. Consider how often someone will want to claim credit for something good or they will want to avoid blame for something adverse. Use of the Z tables can allow us to see what the probability is. We can then apply statistical guidelines for determination of whether what took place was simply due to chance. Here is an example of a company which kept statistics on the number of accidents per month. This could just as easily be medical errors or something like what we saw on the data sets for the radiation therapy department. The monthly data for the two years are shown in Figure 1 , to the right. After seeing that accidents were at 45 for the year, management set a goal of having 25% fewer accidents the next year. Notice, like the pharmacy case, this goal was simply pulled out of the air. Management at this point has no clue as to what the upper or lower range of accidents would be. Nor are they making any changes in the work processes which produced the accidents. After a year went by the data came in at 32, which is 29% fewer. Management felt happier. Note that with the pharmacists, the numbers came in higher. In this accident case management would probably not look further, content that telling people to be safer did the job, just like pharmacy management hoped telling the pharmacists to be more careful would solve the error rate problem. Figure 1
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Page 2 of 16 April 15, 2009 (9:16pm) E:\SWT\HA4315\Class notes\Spring 2009 version\C_24 Spg09.wpd Reduce, reuse, restore, recycle However, the question quality improvement asks is more fundamental. Did the process which produced 45 accidents in one year differ from the process that produced 32 accidents in the second year? If not, then the change may simply have been due to luck. This would be especially likely if management did nothing to change the safety of the system other than set goals. Returning to the accident data, if you look at Figure 2 , to the right, a line chart only is presented. Just looking at the chart it is difficult to see that two different processes are in play for the two different years. We can run additional tests for the presence of a special cause. A. Setting up a run chart using
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This note was uploaded on 03/30/2011 for the course HA 4315 taught by Professor N/a during the Spring '11 term at Texas State.

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Class Twenty Four Notes - Page 1 of 16 Class Twenty Four...

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