Service Design and problem resolution always must be based on the information about the system and environment. How to get such information if we don’t know the exact answer?
(Hubbard, 2010) defines measurement as “a quantitatively expressed reduction of uncertainty based on one or more observations.” So a measurement doesn’t have to eliminate whole uncertainty. “A mere reduction in uncertainty counts as a measurement and possibly can be worth much more than the cost of the measurement.”
Another point here is that uncertainty has to be quantified, “but the subject of observation might not be a quantity itself – it could be entirely qualitative.” For example service quality can be measured as a ratio of customers who use this service more than one time during given period to the total number of the customers.
(Hubbard, 2010) insists that everything can be measured. The logical steps are:
- If it matters at all, it is detectable/observable.
- If it is detectable, it can be detected as an amount (or range of possible amounts).
- If it can be detected as a range of possible amounts, it can be measured
Even if you don’t know the exact values, you still know something. “You know that some values would be impossible or at least highly unlikely. Knowing what you know now about something actually has an important and often surprising impact on how you should measure it or even whether you should measure it… One method to express our uncertainty about a number is to think of it as a range of probable values. In statistics, a range that has a particular chance of containing the correct answer is called a “Confidence Interval” (CI). A 90% CI is a range that has a 90% chance of containing the correct answer.” (Hubbard, 2010)
For example, IT manager can’t know for certain the exact number of requests for support that his division will get next month. However, he can estimate that probably no less than 50 and no more than 150. If the manager is 90% sure the actual number will fall between 50 and 150, then he has the 90% CI of 50-150. This information can already be used for estimation of power that new helpdesk system will require.
The method of 90% CI assessment is subjective. It doesn’t give an accurate result. However, it is based on the real life and professional experience of people as well as their common sense. It decreases uncertainty, and in many cases, 90% CI interval is enough to make a preliminary decision or even to resolve the problem.
(Hubbard, 2010) advices to make some exercises to calibrate 90% CI assessment method and make results more accurate. That should be very useful. However, even if you are not a “calibrated” expert, you still can estimate reasonable interval. So that is much better than no information at all.