
Q?
Why should I buy the CertainError calculator app when my iPhone has free builtin calculator?

A.
Yes, the calculator on your iPhone (or Android device) might be free but, like all handheld scientific calculators, it is not capable of performing automatic error analysis.
With the builtin calculator or scientific calculator, to do a typical error analysis, you first need to learn multivariable calculus or statistics, and then perform a difficult set of calculation steps. Each step could be a place for you to make a mistake. Many people do not perform error analysis because it is difficult, stressful and time consuming.
The CertainError calculator automates this process. You simply enter value and error information, choose the operation or function like you would on a normal calculator and then choose among five different methods. The result is reported as a value and its error, automatically.
After using it on one problem, for example a physics lab, you will see the time and stress saved is well worth the small cost.
For example, assume your teacher wants you to use the common 'Differential' method on a lab experiment because that is the standard method they teach.
You can choose this method on the CertainError calculator so your answers are 'correct' to match what the teacher wants. You do not need to expend the labor doing partial differentials and then somehow organize these formula into a stepby step calculation procedure that can be done on a traditional calculator. The CertainError calculator does it for you following the same steps you would use in the traditional calculator but without the extra steps for error analysis.

Q?
What does the CertainError calculator have that others don't?

A.
First, the CertainError calculator has builtin math to perform simultaneous error propagation.
Above that, it provides the ability of calculating using five different methods (Interval, MonteCarlo, Differential, Chordals and Duals). Standard scientific calculators don’t even have one uncertainty method. The CertainError calculator also contains the traditional calculator so you can check answers ‘without error’ too.
Reaching further, this calculator includes the more sophisticated 'Duals method,' that is not limited to the small errors required by the 'Differential method.'