How valid/reliable are the statistics presented on the evening news?

Question

How valid/reliable are the statistics presented on the evening news?

Answer 1

I'm not sure if your asking about polls or some other statistical data.

If your asking about the political polls, then you should be very skeptical. For many years the pollsters have been using telephone surveys. This was fine when every household had a land line, however today a significant number of new households use cell phones only. Combined with the number of households that screen calls, it has reduced the reliability of these polls.  

Answer 2

The validity and reliable of ANY statistic will depend on its origin and the methodology used to arrive at it. The "evening news" rarely does its own data gathering, so one would have to defer to the source of the data to answer your question. Reputable polling entitities always publish their results with a "margin of error" so you know a little about how their sample was garnered. Other than that, caveat emptor.