Types of Variables. It is very important when designing a research study that the researcher fully understands the variables in the study in order for the results to be valid and have meaning. A variable is something in the study that can be changed such as a characteristic or a value. The most common types of variables, especially when study cause and effect relationships, are the independent and dependent variables. The independent variable is the one that can be controlled or manipulated.
What's the maximum speed you can travel on a freeway with a 65 mph speed limit and be absolutely guaranteed not to get a speeding ticket? 65 mph. That's why it's called a speed limit. Any faster and you will be violating the statute which sets the limit. Now... is it likely you'll get stopped and cited at 66 mph?
Some freeways have fixed point to point cameras 5km apart so you can't beat them by slowing down for the camera as they will get your average speed between the two points - same deal - 3 km over, fine. Cops will pull you over in their vehicles if they detect you speeding anything over about 4kmh over the speed limit. In Australia speed fining is all about blatant government revenue raising - this despite government propaganda calling them safety cameras.