https://www.reddit.com/r/Unity3D/comments/3vuxay/trying_to_make_a_stat_system_help/

PlanePart.cs

using UnityEngine;

public class PlanePart : MonoBehaviour
{
    [Header("Part Stats")]
    public float Attack;
    public float Defense;
    public float Hp;
    public float Weight;

#if UNITY_EDITOR
    // This part allows the inspector to update outside of play mode
    // See: http://docs.unity3d.com/ScriptReference/MonoBehaviour.OnValidate.html
    void OnValidate()
    {
        // Recalculate our stats when they change in the editor
        if (!Application.isPlaying)
        {
            if (gameObject.transform != null && gameObject.transform.parent != null)
            {
                PlaneRoot parent = gameObject.transform.parent.GetComponent<PlaneRoot>();
                if (parent != null)
                {
                    parent.RecalcStats();
                }
                else
                {
                    checkSelf();
                }
            }
            else
            {
                checkSelf();
            }
        }
    }

    // Attempt to find our PlaneRoot and recalculate
    void checkSelf()
    {
        PlaneRoot self = gameObject.GetComponent<PlaneRoot>();
        if (self != null)
        {
            self.RecalcStats();
        }
    }
#endif
}