The fallacy of the linear value of time
So often I see a cost estimate, or worse still a business case, based on the fallacy of the linear value of time. You know the sort: a five minute outage of the service costs $100k; our tool saves five minutes per employee per day which equates to $76M per annum.
The cost of interruption to a service, or the value of time saved, is generally non-linear. (Heck, everything in our physical world is non-linear - a fact often overlooked when forecasting economic recovery, safe levels of biotoxins, sea-level rises, AIDS ...er... penetration, technology adoption...) If a failed service serves office workers then a five minute outage may cost nothing. They stretch, they take a leak, they come back. It is a break they would have taken anyway. It might even boost productivity. A two-hour outage costs much more than 24 times a five-minute outage.
On the other hand if it is a front-office booking system then yes 5 minutes hurts.
Or if it is an automated financial system then you can value 10 seconds of outage.
As Aale Roos said on a LinkedIn discussion about this: My model is to ask the value of different lengths of interruption, for example: 5 min, half an hour, hour, 4 hours, day, several days, month. It is quite unlinear. At one point there can be a big jump.
The same fallacy is used by those who build business cases with an ROI of 5 minutes saved per day for 20,000 employees. Pure B.S.
(Actually safe levels of biotoxins is a real interesting one. Interpolating data from rats force-fed lethal doses of carcinogens to determine a "safe" level for humans is pure scientific silliness and all the scientists know it. The "natural" world is a toxic, carcinogenic, radioactive environment. Our bodies have evolved in it. The one and only shred of truth or sense in homeopathy is the concept that a little of what hurts you does you good. There are experimental indications that low doses of some supposedly harmful substances - or radiation - actually strengthen the body.
Bugs too. Certainly the current obsession with germicidal cleaning agents is pure neurosis. The link between child allergies such as asthma and LACK of exposure to environmental bacteria is now established.
If the safe levels of radioactivity demanded in nuclear facilities applied in the real world, we'd have to evacuate Denver. If California is truly serious about removing carcinogens from the environment, when are they going to ban potatoes, chillies and tomatoes? In fact many foods. Mother Nature is not held to the same exacting standards of trace toxins that our manufacturers are.)