## Quality Assurance vs Quality Control

The difference between Quality Assurance and Quality Control is one of the most frequently asked questions and among the most commonly confused concepts for the PMP exam. Going by the emails and comments I receive, I'm sure many of you are interested in this topic. In this post, we'll look at the differences with the help of a quiz.

## 10 Articles which every PMP Aspirant must Read

When I started this blog last year, the articles were focused on the PMP certification process like how to become a PMP, FAQs, audits etc. As time went on, I started focusing more on exam preparation, tips and study notes. The older posts got buried. For regular visitors, it's not an issue as they know their way around the site well. But for new visitors, who are still finding their feet in the PMP universe, those older posts are more relevant. This article is an attempt to bring those stalwart posts of this blog back on top once again.

## Standard Deviation and Project Duration Estimates

Project Estimation and PERT (Part 9): Standard deviation is a statistical concept that gives a measure of the 'spread' of the values of a random variable around the mean of a distribution. It shows how much variation there is from the average or the mean value. The more the variation, the more the uncertainty or risk in the process. In the article Probability and Statistics in Projects, we learned that PERT assumes that the expected duration of the project follows the normal distribution. By calculating the PERT estimate (mean) and standard deviation of the project duration estimate, we can calculate the probability of completing the project within a given duration. How that works is explained in this article.