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.
Basic Training Academies. The blue markers on the map below represent academies that present POST-certified basic law enforcement training. Click on any of the markers to see the name, address, and website of the academy and get directions to and from the location. Use the movement and zoom controls in the upper left-hand corner to navigate within the map. A list of the academies is available below the map.