You can also set the parameter using scripts. Following is an example script (it is used by the AdjustSpeedByScript game object in the provided Example.unity). You can assign it to your animated game object that has the Animator component and an Animator Controller attached:

using UnityEngine; 
using System.Collections; 
 
public class AdjustSpeedByScript : MonoBehaviour { 
//This is a variable, in which we store the reference to the 
Animator component 
private Animator anim; 
//We store the wanted animation speed in this variable, the 
default value is 2 (200%). 
 
public float newAnimationSpeed = 2f; 
void Start () { 
//At the start of the game we assign the Animator 
component to our anim variable 
anim = GetComponent<Animator>(); 
} 
void Update () { 
//We check if player pressed the Space button 
if (Input.GetKeyDown(KeyCode.Space)) { 
//And set the playback speed of the whole Animator 
Controller (it multiplies all states animation 
playback speed) 
 
anim.speed = newAnimationSpeed; 
} 
} 
} 

If you want to change the speed of just one animation state, then add a float parameter to your Animator Controller, use this parameter in the Multiplier field in the animation state Inspector, and change the parameter with scripts using the following function:

anim.SetFloat(string name, float value); 

Here name is the name of your parameter in the Animator Controller and value is the float value you want to set the parameter and playback speed to.