Originally Posted by 2Loud
If you pull a battery terminal while the car is running and it dies, The alternator is bad, if it continues to run, replace the battery.
The above statement is smart - very smart. (notice a hint of sarcasm here)
One can take a volt meter and determine if there are between 13.5 and 14.5 V @ the battery with engine on (an initial screen test to determine if the alternator needs to be tested) If outside these ranges or if the voltage goes outside these ranges if the lights are turned on too, the odds of a bad alternator are very high or possibly the voltage regulator - either way additional trouble shooting / diagnostics are in order I haven't verified if a 95 Taurus has an internal regulator or an external one or not thus a shop manual would be of great help when doing this kind of trouble shooting.
The only way to diagnose a bad battery is to do a load test.