how to change speed of animations in an array?

I'm trying to put animations in a public array through inspector and then changing speed of every animation in that array in runtime through a public float variable but for some reasons it's not working. Below is my code:

public Animation[] anim;

 [Range(0,2)]
 public float AnimationSpeed;

 public static bool aboard;

 // Update is called once per frame
 void Update () 
 {
     foreach (Animation an in anim)
     {
         anim [anim.Length] [an].speed = AnimationSpeed;
     }
 }

Would be really thankful if somebody could guide me on this issue.

Thanks!