A t-test can be used to account for the uncertainty in the sample variance when the sample size is small and the data are exactly normal. There is no universal constant at which the sample size is generally considered large enough to justify use of the plug-in test. Typical rules of thumb range from 20 to 50 samples.
Each symbol and color in the National Law Enforcement Explorers seal has special significance. 1  The circular form of the seal represents continuous existence. 2  The dominant blue field represents justice. 3  The inner circle contains a shield surmounted by an eagle.
The colors indicate the speed of traffic on the road. 1  Green means there are no traffic delays. 2  Orange means there's a medium amount of traffic. 3  Red means there are traffic delays. The more red, the slower the speed of traffic on the road.