Spawn Script

This is my script:

using UnityEngine;
using System.Collections;

public class Spwn: MonoBehaviour {
	
	public GameObject[] obj;
	public float spawnMin = 1f;
	public float sapwnMax =2f;
	
	void Start (){
		Spawn();
	}
	void Spawn (){
		Instantiate(obj[Random.Range (0,obj.GetLength(0))], transform.position, Quaternion.identity);
		Invoke ("Spawn", Random.Range (spawnMin, sapwnMax));
	} 
}

Is there a way that some game objects have more chances to spawn them others ?

One approach:

void Spawn (){

  // Get a random number from 0 - 100.
  float rand = Random.Range(0f, 100f);

  if(rand < 30) {
    // 30% chance of creating obj[0]
    Instantiate(obj[0], transform.position, Quaternion.identity);
  }

  else if(rand < 80) {
    // 50% chance of creating obj[1]
    Instantiate(obj[1], transform.position, Quaternion.identity);
  }

  else {
    // 20% chance of creating obj[2]
    Instantiate(obj[2], transform.position, Quaternion.identity);
  }

  Invoke ("Spawn", Random.Range (spawnMin, sapwnMax));

}