Possible double (1B coach's responsibility)

On a batted ball to the outfield the 1B coach has a responsibility to communicate very important information to the batter/runner rounding 1st base. The 1B should be screaming at him how many outs there are. It is absolutely not the 1B coach's responsibility to tell the runner whether or not he should attempt to get to 2B. It is the coach's responsibility to inform the runner of the risk/reward scenario.

A general baseball rule is that you should try and get into scoring position with 2 outs. Many, many times it is deemed appropriate if you are thrown out going to 2B for the 3rd out. You are simply trying to get into scoring position so you can score on a hit with two outs. Therefore, on a hit to the outfield the 1B coach screams the number of outs as they are rounding 1B. If the coach yells "2 outs, 2 outs!" the runner is thinking I should try and get into scoring position.

If the coach yells "nobody, nobody" the runner is aware that he is leading off the inning. Most coaches like a baserunner anywhere with nobody out. They don't want inning killers so this information makes the runner a lot more cautious. Predictably, if the 1B coach yells "1 out, 1 out" the runner is aware of the outs and is a little more cautious. The runner isn't thinking "definitely 2B" but he isn't nearly as cautious as if there were nobody out.

I think it is very important for the 1B coach to express to the runner how many outs there are rather than telling them to go or not go(the exception being when you're running into an out). The speed of the runner, the angle the outfielder takes to the ball, the arm strength of the outfielder should help guide the runner rounding 1st base. The 1B coach mentioning the outs is a subtle reminder as to how aggressive the runner should be.