Statistics calculation shortcuts and probability hacks?

[RyanAP]

Working with data analysis daily, I've collected some statistics calculation shortcuts that save hours. Things like quick variance approximations and probability calculation hacks for common distributions.

What statistics calculation shortcuts do you use regularly? I'm also interested in mathematical pattern recognition shortcuts that help identify distributions faster. Any unit conversion memory tricks that work well with statistical data?

[TylerM]

For statistics calculation shortcuts, the empirical rule (68-95-99.7) for normal distributions saves time. Approximately 68% within 1 SD, 95% within 2 SD, 99.7% within 3 SD of the mean.

Also, for probability calculation hacks with coins or dice, remember that probability = favorable outcomes / total outcomes. But for independent events, multiply probabilities.

[Scarlett71]

Standard deviation shortcuts: for a sample, use n-1 in denominator. For a population, use n. Remembering which is which saves time.

Also, for correlation coefficient ®, it ranges from -1 to 1. Values closer to ±1 indicate stronger linear relationships. This quick check helps interpret results faster.

[PatrickRT]

For probability calculation hacks with combinations and permutations, remember: permutations order matters, combinations order doesn't. Use nPr for permutations, nCr for combinations.

The factorial shortcut: n! = n × (n-1) × ... × 1. But 0! = 1 and 1! = 1. These basics save time on complex problems.

[Avery90]

Unit conversion memory tricks: for metric prefixes, remember King Henry Died By Drinking Chocolate Milk" (kilo, hecto, deca, base, deci, centi, milli). Each step is a factor of 10.

For temperature, °C to °F: F = (9/5)C + 32. Or approximate: double C and add 30 (close enough for mental math).

[Logan43]

These statistics calculation shortcuts and probability calculation hacks are really helpful for my stats class. The empirical rule shortcut is something I use all the time now.

What about mathematical pattern recognition shortcuts for identifying which statistical test to use? That's where I get stuck.