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References Category:Aviation licenses and certificationsQ: Does a table or a database thread application scale? I have a scenario here where I am working with a database for the first time. I did some research and came across articles that talk about the pros/cons of a database vs. a thread-based architecture. My current requirements are as follows: I have two threads to access the same table in the database. The thread accessing the database needs to “lock” and “unlock” data to be accepted/rejected from users If data is accepted and the user were to change the data (by inserting/updating/deleting), any other threads that the user can be in that same table would need to be aware of the changes and accept/reject the changes as well. So I’m thinking in terms of table-per-thread but after reading some articles I don’t know if that’s the right route to take. A: Scale? Not sure what you mean by that, but… Depending on the size of the data that you are working with, you can have a single, and very large, database table that has one column containing the last ID used and a row lock. You can do many operations on the table without the lock getting in the way, and you can process those that are “finished” in the background using the ID and a thread. If the data is not huge, and your threads are not very busy, you could use a single database and a few tables that lock for individual threads to be able to work on them without that hindering the performance. Your article is a bit older, so as database system and programming has evolved, I’d say that scaling is less of an issue and more about what you are trying to achieve. Q: Why is coefficient of variation of std. dev. not constant In D. McCloskey’s Introduction to Modern Probability, the coefficient of variation is defined as $cv = \frac{\sigma}{\mu}$ where $\mu$ is the mean and $\sigma$ is the standard deviation. However, the standard deviation is itself a random variable. Therefore the coefficient of variation is random, too. Now, it is usually clear why, e.g. $cv$ is non-negative, but I do not quite see why \$