To calculate the standard deviation of those numbers: 1  1. 2  Work out the Mean (the simple average of the numbers). 3  2. Then for each number: subtract the Mean and square the result.4  3. Then work out the mean of those squared differences.5  4. Take the square root of that and we are done!o calculate the standard deviation of those numbers: 1  1. 2  Work out the Mean (the simple average of the numbers). 3  2. Then for each number: subtract the Mean and square the result.
FBF = Flashback Friday. #FBF is an acronym primarily used on Instagram, Facebook, Twitter, and Tumblr that stands for Flashback Friday. Users typically use the tag on photos of moments in their past, like last yearâs vacation or a childhood friend.
For something that cannot be repaired, the correct term is Mean Time To Failure (MTTF). Some would define MTBF â for repair-able devices â as the sum of MTTF plus MTTR. .In other words, the mean time between failures is the time from one failure to another. This distinction is important if the repair time is a significant fraction of MTTF. Here is an example.