Statistics for Management and Economics 10th Keller 课后答案SME10e_SM_ch21

1、Chapter 2121.1Chance variation is caused by a number of randomly occurring events that are part of the production process and that in general cannot be eliminated without changing the process. 21.3 Special variation is caused by specific events or factors that are frequently temporary and that can u

2、sually be identified and eliminated21.4a Chance variation represents the variation in student achievement caused by differences in preparation, motivation, and ability.b Special variation represents variation due to specific event or factors that can be corrected. 21.5 21.6 ARL = = 8121.7 21.8 ARL =

3、 = 2221.9 ARL = = 385Number of units = Production ARL = 100(385) = 38,50021.10a From Beta-mean spreadsheet, = .6603b Probability = .6603= .036121.11 P = 1 = 1 .6603 = .3397; ARL = = 2.9421.12 Number of units = Production ARL = 50(385) = 19,25021.13a From Beta-mean spreadsheet, = .8133b Probability =

4、 .8133= .191421.14 P = 1 = 1 .8133 = .1867; ARL = = 5.3621.15 Sampling 3 units per hour means that on average we will produce 38,500 units before erroneously concluding that the process is out of control when it isnt. Sampling 2 units per half hour reduces this figure by 50%. Sampling 4 units per ho

5、ur means that when the process goes out of control, the probability of not detecting a shift of 1.5 standard deviations is .6603 and we will produce on average 2.94 100 = 294 units until the chart indicates a problem. Sampling 2 units per half hour increases the probability of not detecting the shif

6、t to .8133 and decreases the average number of units produced when the process is out of control to 50 5.36 = 268.21.16 Number of units = Production ARL = 2000(385) = 770,00021.17a From Beta-mean spreadsheet, = .7388b Probability = .7388= .297921.18 P = 1 = 1 .7388 = .2612; ARL = = 3.8321.19 Number

7、of units = Production ARL = 4000(385) = 1,540,00021.20a From Beta-mean spreadsheet, = .3659b Probability = .3659= .017921.21 P = 1 = 1 .3659 = .6341; ARL = = 1.5821.22 Sampling 10 units per half hour means that on average we will produce 770,000 units before erroneously concluding that the process i

8、s out of control when it isnt. Sampling 20 units per hour doubles this figure. Sampling 10 units per half hour means that when the process goes out of control, the probability of not detecting a shift of .75 standard deviations is .7388 and we will produce on average 3.83 2000 = 7660 units until the

9、 chart indicates a problem. Sampling 20 units per hour decreases the probability of not detecting the shift to .3659 and decreases the average number of units produced when the process is out of control to 4000 1.58 = 6320.21.23 Centerline = = 453.6Lower control limit = = 453.6 3= 434.85Upper contro

10、l limit = = 453.6 + 3= 472.3521.24 Centerline = = 181.1Lower control limit = = 181.1 3= 170.1Upper control limit = = 181.1 + 3= 192.1Zone boundaries: 170.10, 173.77, 177.44, 181.10, 184.77, 188.43, 192.1021.25 a Centerline = = 13.3Lower control limit = = 13.3 3= 7.6Upper control limit = = 13.3 + 3=

11、19.0c The process is out of control at points 8, 9, 21, 22, and 25.21.26a S Chart Chartc The process is out of control at samples 29 and 30.d A level shift occurred.21.27a S Chartb The process is out of control at the first sample.c Clean out the sawdust more frequently.21.28The process is under con

12、trol.21.29 = 1.0021.30The process is under control.21.31 = 1.6921.32a The process is out of control.b The process is out of control at sample 19.c The width became too small.21.33The process is out of control at sample 21. It is not necessary to draw the chart.21.34The process is out of control at s

13、ample 23. It is not necessary to draw the chart.21.35The process is under control.21.36 = .9221.37The process went out of control at sample 23.21.38The process went out of control at sample 29.21.39ab The process went out of control at sample 2521.40The process is under control.21.41 = .7121.42 = .5

14、3The value of the index is low because the statistics used to calculate the control limits and centerline were taken when the process was out of control.21.43 Centerline = = .035Lower control limit = = .035 = .0174Upper control limit = + = .035 + = .052421.44 Centerline = = .0324Lower control limit

15、= = .0324 = .00516 (= 0)Upper control limit = + = .0324 + = .06996The process is out of control at sample 25.21.45 Centerline = = .00352Lower control limit = = .00352 = .00443 (=0)Upper control limit = + = .00352 + = .01147The process is under control.21.46 Centerline = = . 0383Lower control limit =

16、 = .0383 = .0193 (= 0)Upper control limit = + = .0383 + = .0959The process is out of control at samples 25 and 30.21.47 Centerline = = .0169Lower control limit = = .0169 = .0047Upper control limit = + = .0169 + = .0291The process is out of control at samples 37-40.21.48 The process is out of control at sample 28.21.49 The process went out of control at sample 9.21.50 The process is out of control at sample 24.