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Operational Research

You can always be more efficient

Operational Research is all about using analysis to improve decision making. Dr Angela Moore uses mathematical modeling, statistical analysis, optimisation, sequencing and scheduling techniques to create simple heuristics you can employ to run your operation more efficiently.

angela@oranalysts.com

Blog

Covering for Sickness

Wednesday, 09 May 2012 14:47

Now everyone knows about sickness rates, where the average is 2.5-3%. But the real question is what this sickness rate means to the operation? Well this is a very complicated question. Firstly you have to consider how the sickness rate is created. Normally it is calculated by the number of sickness hours per year divided by the contracted hours. Well this is a very useful statistic if you want to know how many hours a group of staff will be sick for each year. But it does include both long term and short term sickness as well as sickness at work and on holidays. So when it comes to arranging cover for these absences, you may not treat all of these cases the same. For instance if someone is going to have an operation, it will normally be booked a long time in advance. And you would know if they were likely to be back at work soon after the operation or if they would need recovery time. So you would not arrange cover for this type of absence in the same way you would deal with covering for a shift where someone fell ill at work.

Secondly, the danger with statistics is that they need to be used within a context. So at a university for example you will have a large range of diverse staff. Now if the university just has one sickness rate this can mislead you when organising cover for a specific department. After all the lecturers may have an average absence rate because they are mixing with students all the time and catching every bug, yet the job is low risk. The administration may have a very low sickness rate because they have a risk free job. The security department may have a high absence rate because of the risk involved with the work. So you need to know the absence rate for the department if possible.14 Staff

Thirdly, to minimise the disruption to the operation you would use this average statistic to create a cover arrangement. So if the statistic says that you have a 5% sickness rate how many times will one person be absent off a shift.  How many people will need to be on cover per shift to ensure you will always have the correct number on duty? How any people to ensure that 90% of the time?

Well the answer is not as straight forward as you would think. Let’s say the operation is 24/7, 12-hour shifts with 14 on duty per shift. The graph shows the number of people that will be off a percentage of shifts for a 5% absence rate. With 12 hour shifts, 24/7 there would be 730 shifts per year. So on less than 50% of the shifts no one will be absent. You would expect one person to be absent on 36% of the shifts, that’s 252 shifts per year. You could have up to four people absent on any shift, and you would expect that to happen three times per year. You would need three people on cover every day to ensure that 90% of the time you had the correct minimum staffing numbers. That’s will cost 11% extra in labour charges for 5% absence. Three extra would give you the correct minimum staffing levels on 95% days. This would still leave you short on 18 days per year.

This sort of analysis is vital for ensuring you have the correct number of staff when and where you want them. We do this analysis as part of our Business Health Check, and whenever we set up a new shift pattern.

 

Global Shift Patterns

Friday, 04 May 2012 14:33

When you have a global organisation and some operations require individuals from around the world working together you can create a global shift pattern. One organisation we recently worked with wanted to combine their European and American call centres. They wanted to keep both sets of workers but have them working together even though they were in different time zones. This meant that the teams would work together and through the use of video links would be able to communicate with each other during the shift, as if they were in the same office.

The advantage of this operation is that the workloads for the two call centres were different.  This was due to the time zone differences, and the workload was random, so predicting the workload and having additional operators during busy times was impractical. Since the probability of both call centres being busy at the same time was low, combining the workload was an ideal solution to doubling up both call centres. So now if a call came in from America or Europe it could be answered by either team and reduce call waiting times.

However a shift pattern had to be devised so that the two teams could work together and that the time difference did not mean that the shifts started and finished in the middle of the night. The two groups were put onto the same shift pattern but with different start and finish times, the holidays were incorporated to minimise disruption and cover arrangements were made between the two teams so that the Americans could cover for the Europeans in case of sickness.

The result was, lower call waiting times, lower workloads for both teams, better communication globally, more quality time off, more opportunities for training and project work.

 

Incorporating Regular Overtime

Thursday, 26 April 2012 12:39

One way to cope with holidays and absences is to use overtime. The advantages of this are that you don’t need to employ additional workers or train up individuals if the skill set is rare. The disadvantages are that it is expensive with overtime rates usually being between 1.5 to 2 times basic rate, and there is the problem of overworking the individuals. When an individual is already working between 37 to 48 hours per week, creating a shift pattern which gives the individual a good work-life balance, meets the Working Time Directive, and allows for additional overtime, can be problematic.

DDCNN Shift Pattern

We have created four different shift patterns to cope with this. Using 8-hour shifts you extend the shifts on each side of the missing shift by 4 hours to cover.   Using 12-hour shifts it is often impractical to extend the shifts therefore whole cover shifts must be added. On the 232 shift pattern the cover shifts are worked between the days and nights, so that both day and night shifts can be covered. This allows an individual to work up to 63 hours per week regularly. However they will be working up to seven consecutive shifts.  On the 3on-3off shift pattern again the cover shifts can be worked between the day and night shifts. Again this allows the individual to work up to 63 hours per week regularly. However they will be working up to nine consecutive shifts.  The fourth option is a shift pattern based on the 4on-4off, this shift pattern is depicted on the right. The individual works two days, one cover, two nights, three off. This is an eight day rotation and allows an individual to work up to 52.5 hours per week regularly. However they will only be working up to five consecutive shifts.

On all of these options everyone does not have to work all of the overtime shifts every week. Individuals can select a proportion of overtime shifts they would be willing to work each year; these are then incorporated into the shift pattern at the start of the year. This way the company always has overtime shifts available and the shift workers always have guaranteed dates when they will not be required to work.

 

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