How to Validate your Decisions Using Statistics (Analysis of Variance) – Part II

crossroadsIn the previous post I showed how to solve a simple problem by performing an Analysis of Variance (if you haven’t read it, please click here). The example was about three different methods to perform a task and we wanted to know if we are getting different results or the variations on the data are only due to the population dispersion.

Generally speaking, we compared the variances between the three samples and the variances within each sample and used the Variance Ratio Test to know, with a specific confidence interval, if the samples are coming from the same population, which in practical terms (referred to our example) means that the different methods are not changing the outcomes. In our example we rejected this hypothesis, so we can say that there is a significant difference between the methods. Continue reading

Maintainability and its relation with reliability and maintenance

Relations between Maintainability - Reliability - MaintenanceAll people involved in maintenance activities know that some equipment are really easy to maintain while others can make maintenance work a real nightmare. This attribute is referred as maintainability and I’m going to discuss it and relate it to maintenance, reliability and availability concepts.
I will start by simply defining the different terms, you can skip this section if you are already familiar with them. Continue reading