The Speedway Clinical Laboratory is a scientific blood-testing facility that rec

Question

The Speedway Clinical Laboratory is a scientific blood-testing facility that receives samples from local hospitals and clinics. The blood samples are passed through several automated tests and the results are printed through a central computer that reads and stores the information about each sample that is tested. Management is concerned about the quality of the service it provides and wants to establish quality-control limits as a measure for quality of its tests. Such managerial practice is viewed as significant, because incorrect analysis of a sample can lead to a wrong diagnosis by the physician, which in turn might cost the life of a patient. For this reason, 100 blood samples were collected at random each day after they had gone through testing. After retesting was performed manually on this sample, the results were: Determine the upper and lower control limits for a p-chart to be used in assessing the quality of the service described above On average, what is the expected number of incorrect tests per 100 samples? Later another sample of 100 was taken After the accuracy of the tests was established, 10 samples were found to have been analyzed incorrectly What is your conclusion about the quality of the service? What recommendations can you suggest?

Explanation / Answer

  (a) UCL = 0.0755 and LCL = 0.0005 (assumed at 95% confidence level)

(b) on Average, the expected number of incorrect test per 100 sample = p bar * 100 = 0.038* 100 = 3.8

(c) If 10 samples found incorrect in sample size of 100 means incorrect analysis rate = 10/100 = 0.1, it is not coming between the UCL and LCL therefore not acceptable. the process in not in control limits.

Days Incorrect Analysis Sample size Incorrect Analysis rate 1 8 100 0.080 2 3 100 0.030 3 1 100 0.010 4 0 100 0.000 5 4 100 0.040 6 2 100 0.020 7 9 100 0.090 8 6 100 0.060 9 3 100 0.030 10 1 100 0.010 11 4 100 0.040 12 6 100 0.060 13 5 100 0.050 14 10 100 0.100 15 2 100 0.020 16 1 100 0.010 17 0 100 0.000 18 6 100 0.060 19 3 100 0.030 20 2 100 0.020 Total 76 2000 P bar (total Number of incorrect analysis/ total sample) 0.0380 Sp (sqrt (P bar*(1- p bar)/100) 0.0191 z (assumed at 95%) 1.96 UCL (p bar + z* Sp) 0.0755 LCL (p bar - z* Sp 0.0005

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