The world around us is full of uncertainties. In research, in engineering and sciences, uncertainties must be dealt with in a formalized way, using statistics. We are required to follow procedures for dealing with inevitable variation in routine testing: in laboratory, in production and construction, in relation to quality control and quality assurance issues.
Excel statistical functions help in solving many practical problems in that area, as well as in simulation and estimation of probabilities of certain outcomes. Here I just like to share with you couple of charts based on simulation I've carried out in Excel regarding the critical role of sampling frequency and the number of tested samples in evaluation of various processes and material properties.
The simulation example shown below is based on assumption of normal distribution of sampling and uses two basic statistical functions:
- RAND() , which returns evenly distributed random numbers from 0 to 1 (not including 1), and
- NORM.INV, which returns the inverse of the normal cumulative distribution for the specified arithmetic mean and standard deviation.