Inventory Management Homework Set  You work in the administration of a major hospital.  One of your tasks is the scheduling of one of the operating rooms in the hospital. The room is used for a specific elective surgery. You allocate a certain amount of time for a surgery; if the actual duration of the surgery exceeds the allocated time, the surgery scheduled next has to start later, and this usually results in overtime at the end of the day where surgery personnel have to stay late into the evening hours. If the actual duration of the surgery is less than the allocated time, the operating rooms remains idle until the next scheduled surgery, since the required resources for the surgery to start (staff, surgeon, equipment, patient) do not become available earlier. You currently allocate 90 minutes for each surgery (from the beginning until the room is ready for the next patient). However, surgeons and personnel have voiced their opinion that they believe this is not enough time – too often do they run over, and too often do they have to stay late to resolve schedule overruns. The higher levels of the administration agree, since overtime work is generally associated with higher costs as well as possibly worse patient outcomes. You decide to manage this process more rigorously, and download data on 200 completed surgeries that contains information on the actual durations of the surgeries (beginning until the room is ready again), as well as some data on which surgery team was involved, and some patient specific data (Body Mass Index, or BMI of patient), see Surgery Data.xls. Question 1 : Your higher level managers in the hospital tell you that surgeries should finish within the allocated time 99% of all times. Calculate the amount of time you should allocate per surgery to make that happen. How much safety buffer is included in this number? ( Note that the safety buffer is the difference between your allocated time, and the time it would take to complete the surgery on average ) Question 2 : You try to understand the precise cost factors associated with allocating too much and too little time to a surgery. While opinions diverge, most of your colleagues tell you that a minute of being overtime is about 3 times as bad as a minute of finishing early. Can you use this information to revise how much total time (and buffer time) you would allocate to a surgery? Question 3 : One of the surgery teams (let’s leave it unspecified which one!) likes to schedule surgeries in continuous blocks. They tell you that they can handle three surgeries in a row; according to them, an advantage would be that all resources to start the next surgery early, in case they are done early, would be available. How much time would you allocate to such a block of three surgeries in a row (under the cost information from Q2)? Compare this time to the time you would normally allocate to three surgeries made by three different teams. How much buffer time can you save .

1. Inventory Management Homework Set
You work in the administration of a major hospital. One of
your tasks is the scheduling of one of the operating rooms in the
hospital. The room is used for a specific elective surgery. You
allocate a certain amount of time for a surgery; if the actual
duration of the surgery exceeds the allocated time, the surgery
scheduled next has to start later, and this usually results in
overtime at the end of the day where surgery personnel have to
stay late into the evening hours. If the actual duration of the
surgery is less than the allocated time, the operating rooms
remains idle until the next scheduled surgery, since the required
resources for the surgery to start (staff, surgeon, equipment,
patient) do not become available earlier.
You currently allocate 90 minutes for each surgery (from the
beginning until the room is ready for the next patient).
However, surgeons and personnel have voiced their opinion that
they believe this is not enough time – too often do they run
over, and too often do they have to stay late to resolve schedule
overruns. The higher levels of the administration agree, since
overtime work is generally associated with higher costs as well
as possibly worse patient outcomes. You decide to manage this
process more rigorously, and download data on 200 completed
surgeries that contains information on the actual durations of
the surgeries (beginning until the room is ready again), as well
as some data on which surgery team was involved, and some
patient specific data (Body Mass Index, or BMI of patient), see
Surgery Data.xls.
Question 1
: Your higher level managers in the hospital tell you that
surgeries should finish within the allocated time 99% of all

2. times. Calculate the amount of time you should allocate per
surgery to make that happen. How much safety buffer is
included in this number? (
Note that the safety buffer is the difference between your
allocated time, and the time it would take to complete the
surgery on average
)
Question 2
: You try to understand the precise cost factors associated with
allocating too much and too little time to a surgery. While
opinions diverge, most of your colleagues tell you that a minute
of being overtime is about 3 times as bad as a minute of
finishing early. Can you use this information to revise how
much total time (and buffer time) you would allocate to a
surgery?
Question 3
: One of the surgery teams (let’s leave it unspecified which
one!) likes to schedule surgeries in continuous blocks. They tell
you that they can handle three surgeries in a row; according to
them, an advantage would be that all resources to start the next
surgery early, in case they are done early, would be available.
How much time would you allocate to such a block of three
surgeries in a row (under the cost information from Q2)?
Compare this time to the time you would normally allocate to
three surgeries made by three different teams. How much buffer
time can you save by blocking surgeries this way?
Question 4
: The dataset contains both surgery team and patient level
information. You get a sense that – since this information is
available upfront – you could create better estimates on how

3. long a surgery will take by making use of this information.
Using regression analysis, can you show whether or not the
specific surgery team involved and the body mass index of the
patient influence the duration of a particular surgery? By how
many minutes would you be able to reduce the buffer time in a
surgery (under the cost information from Q2) by making use of
this information?
DATA SET
Surgery ID
Surgery Duration
Surgery Team
BMI of Patient
1
49
3
29
2
46
2
29
3
93
2
28
4
85
1
24
5
93
2
30

4. 6
157
4
29
7
100
2
28
8
70
3
24
9
64
2
23
10
99
1
24
11
131
3
23
12
66
4
22
13
108
4
31
14
86
4
18

5. 15
117
2
27
16
72
4
22
17
127
2
28
18
127
1
20
19
86
2
25
20
93
4
25
21
111
4
18
22
114
4
36
23
91
2
28

6. 24
83
2
23
25
100
1
25
26
72
3
22
27
72
2
15
28
109
4
28
29
91
2
21
30
124
2
27
31
27
1
24
32
78
1
17

7. 33
190
1
37
34
57
3
18
35
97
3
15
36
31
1
25
37
80
4
29
38
55
3
23
39
116
3
33
40
92
2
21
41
74
1
20

8. 42
129
2
27
43
39
2
29
44
42
3
32
45
89
2
30
46
115
1
24
47
84
1
20
48
107
4
37
49
120
4
25
50
96
3
16

9. 51
106
4
27
52
124
1
22
53
54
2
19
54
135
3
32
55
82
2
24
56
88
1
22
57
66
3
27
58
84
1
27
59
69
2
23

10. 60
71
1
25
61
87
3
24
62
149
2
29
63
125
1
21
64
92
2
20
65
21
4
22
66
90
1
24
67
55
4
20
68
126
1
28

11. 69
126
3
19
70
115
4
29
71
123
3
27
72
62
3
24
73
96
3
25
74
79
2
26
75
79
4
23
76
91
1
12
77
37
2
17

12. 78
61
3
22
79
93
4
29
80
76
3
20
81
73
4
20
82
105
1
35
83
72
3
26
84
105
3
29
85
107
2
25
86
92
3
25

13. 87
94
1
13
88
102
4
20
89
91
3
18
90
42
4
19
91
103
1
21
92
111
3
20
93
109
1
22
94
128
3
23
95
115
4
29

14. 96
67
3
25
97
75
3
13
98
85
2
24
99
117
2
21
100
152
2
24
101
96
2
25
102
28
1
20
103
124
4
21
104
18
2
24

15. 105
85
4
25
106
114
4
22
107
43
4
27
108
109
2
23
109
25
4
27
110
67
4
19
111
113
1
25
112
67
4
30
113
116
4
29

16. 114
32
4
12
115
42
2
29
116
153
1
29
117
32
2
33
118
63
3
18
119
102
3
22
120
122
1
26
121
68
1
26
122
110
4
31

17. 123
38
3
30
124
158
1
31
125
63
2
28
126
102
1
32
127
92
4
22
128
113
2
17
129
129
4
18
130
154
2
20
131
87
4
24

18. 132
97
1
24
133
122
1
22
134
46
2
25
135
110
2
26
136
33
3
25
137
104
3
28
138
36
3
25
139
116
2
21
140
69
3
29

19. 141
70
3
20
142
115
3
27
143
123
3
28
144
174
1
34
145
120
2
27
146
120
1
24
147
101
4
30
148
75
2
24
149
72
3
20

20. 150
124
4
23
151
56
2
20
152
103
1
29
153
86
1
21
154
55
4
17
155
65
2
19
156
86
2
28
157
175
2
36
158
67
2
27

21. 159
79
2
22
160
29
4
21
161
82
2
26
162
132
2
28
163
72
1
13
164
144
2
28
165
132
1
26
166
117
1
28
167
63
3
27

22. 168
58
4
32
169
88
3
25
170
108
3
23
171
80
2
33
172
103
4
21
173
149
1
25
174
102
3
23
175
138
1
31
176
77
4
29

23. 177
115
4
21
178
134
4
20
179
81
4
16
180
99
2
25
181
76
2
24
182
91
4
22
183
138
1
24
184
42
2
22
185
104
3
27

24. 186
66
3
30
187
109
4
35
188
103
4
19
189
69
3
21
190
81
3
26
191
122
1
27
192
77
1
24
193
55
1
26
194
60
4
19

25. 195
105
1
29
196
86
2
22
197
75
4
21
198
49
4
14
199
73
3
25
200
93
2
28