介绍莫斯特卡斯特综合医院有一个繁忙的事故和急诊(A&E)部门(请注意：在某些国家/地区，这简称为急诊科)。 目前，由于患者经常需要在A&E中等待很长时间，因此其性能尚不令人满意。 目前，员工人数的时间表因各种因素(例如，员工人数，假期等)而每天变化。医院计划招聘一些额外的员工，但它不知道需要多少员工。医院想知道在一天中的不同时间应该有多少员工才能取得良好的绩效。

　　急诊科医院为您提供了有关急诊科当前工作方式的以下信息：急症室有两种类型的患者：紧急患者和非紧急患者。 患者在急症室接受各种治疗和评估，然后离开。 离开急症室称为“出院”。 病人可能会把急症室(A&E)送到各个目的地，例如，他们可能会回家，去另一个护理提供者(例如护理院)或去医院的病房。患者随机进入急诊室。 在几周内的三个时间间隔内对到达的患者总数进行了计数。 时间间隔的平均值如下：

Time interval	Non-urgent	Urgent
Midnight – 8 a.m.	48	1
8 a.m. – 4 p.m.	128	4
4 p.m. – midnight	80	2

例如，这意味着在午夜至上午8点之间平均有48名非紧急患者和1名紧急患者到达。紧急患者受重伤，通常是通过救护车到达的。 当他们到达时，他们会得到紧急护理(例如复苏)。 他们到达后必须立即进行。 如有必要，执行其他任务的医生将停止他们正在做的事情以提供紧急护理。 医院仅设有可同时为三名患者提供紧急护理的设施。 如果有三名患者接受紧急护理治疗，并且发生另一例紧急情况，那么该患者将被送往另一家医院。 紧急护理时间的数据平均为60分钟，标准差为20分钟。 对数正态分布对于该数据被认为是现实的。如果医生停止执行提供紧急护理的任务，那么任何医生都可以完成该任务-即另一位医生可以完成原始任务。在接受紧急护理后，有60%的紧急患者离开急诊室并出院(通常去医院的病房)。 40%的紧急患者在A&E中接受进一步治疗。这种治疗不需要立即进行，但它确实比非紧急患者优先。治疗后，这些患者随后被出院(通常再次送往医院病房)。紧急患者在A&E中最多接受一种治疗活动。这些处理时间的数据平均为30分钟，标准偏差为15分钟。对数正态分布也被认为对该数据是现实的。非紧急患者有各种情况或受伤，需要通过“分类”程序来处理。首先，患者会见接待人员(1人)并进行登记(记录其姓名和个人详细信息)。此活动所用时间的唯一可用信息是估计的最小值为1.5分钟，模式为2.5分钟，最大值为5分钟。然后，他们会见分诊护士，对患者进行初步评估。此活动所用时间的唯一可用信息是估计的最小值为3分钟，模式为5分钟，最大值为10分钟。见到分诊护士后，一些病人已出院。如果他们没有出院，患者接下来会去看医生进行更详细的评估。在看医生之后，有些患者必须在A&E中从医生那里得到特定的治疗(例如医疗程序或扫描)。活动的顺序是患者总是交替看医生并得到治疗。患者在A&E中最多接受两种治疗和三种医生评估。这些活动中的任何一项都可能被释放。百分比如下：

Stage	% to next process	% discharged
Triage	80%	20%
1st doctor assessment	70%	30%
1st treatment	80%	20%
2nd doctor assessment	25%	75%
2nd treatment	50%	50%
3rd doctor assessment	0%	100%

　　The times for the doctor assessments are believed to follow a lognormal distribution. The times for the 1st assessment have mean of 15 minutes and a standard deviation of 4 minutes. The times for the 2nd assessment have a mean of 12 minutes and a standard deviation of 6 minutes. The times for the 3rd assessment also have a mean of 12 minutes and a standard deviation of 6 minutes.

　　The times for the treatments have not been analysed. However, a spreadsheet containing a sample of 100 treatment times is provided on Moodle with this document. It is believed that there is no difference in the distribution of times for 1st and 2nd treatments.

　　Staff work shifts of: midnight – 8 a.m., 8 a.m. – 4 p.m., 4 p.m. – midnight. The hospital can schedule any number of nurses and doctors to each shift. A nurse costs 0.6 of the cost of a doctor. The standard pay rate applies to the shift of 8 a.m. – 4 p.m. Doctors and nurses working on the shift from midnight – 8 a.m. receive extra pay and cost an additional 30%, those working on the shift from 4 p.m. – midnight cost an additional 20%.

　　The triage assessments are done by nurses. The doctor assessments and the treatments for urgent and non-urgent patients are all provided by doctors. Although there are different types and levels of doctor, at this stage the hospital would just like to know the total number of doctors required (i.e., assume that the doctors can carry out any assessments and treatments). Also assume that each assessment and treatment is provided by one doctor (i.e., doctors work alone).

　　The availability of space and facilities mean that there are maximum numbers for each process that can simultaneously take place at any one time. The maximum number of triage assessments is 5, the maximum number of doctor assessments is 6, the maximum number of non-urgent treatments is 6, the maximum number of urgent care is 3, the maximum number of urgent treatments is 3.

　　Patients wait between processes in the waiting area. There is plenty of space in this area.

　　The current government performance target is that 95% of patients should be discharged from A&E within 4 hours of arriving at A&E. The hospital aims to meet this target. It is possible in the future that 90% might be considered acceptable and the hospital would like to know what difference it would make if they use this target instead. The hospital would like to minimise staff costs whilst providing a good service. They are also interested in any other useful measures of performance although they are not sure what these might be.

　　Your task

　　The hospital know that you have expertise in simulation modelling and they would like you to build a simulation model of the A&E department and to use the model to provide advice on how they should run the department. Your report should include specific recommendations on what the hospital should do.

　　No other information is available at the moment and so you will need to base your analysis on the above description of the system. State any assumptions that you make about the system. You should build your own simulation model starting with the blank Witness Startup model.

　　The hospital may be able to obtain more information and data that could be used for further work on the model over the summer, although they are not sure what would be useful. Please include in your report an explanation of what further data would be helpful and how you would use it. The hospital are also interested in knowing about any limitations of the model and your analysis.

　　Simulation software

　　You must use the Witness simulation software for your model.

　　Submission

　　Each group is required to submit the following two items through Moodle. Only one person in the group needs to submit the files (do not submit the files several times under the different people in the group).

　　• A written group report as a Microsoft Word document describing the project. The maximum length of the report (excluding appendices) is 5000 words. You can assume that the reader of the report is familiar with simulation. Hence, you do not need to explain general simulation concepts or simulation terminology. You need to explain clearly how your model works and what you did for each of the simulation tasks. Credit can only be given based on what you put in the report and so allow enough time for writing the report. Some analysis can be included in an appendix but do not include many pages of model code or statistical output in the appendices without any explanation in the report.

　　• A Witness simulation model file containing a working version of your model.

　　This is the submission deadline and any submission after this deadline is subject to standard departmental penalties, unless you have been given an extension for exceptional reasons. The extension must be granted by me before the deadline.