Twice I've attacked a creeper with my sword, which has sharpness and knockback enchantments, and twice whilst still far away from me it's exploded.
Is this coincidence or does the knock back set the creeper off/not reset the distance from Steve?
Minecraft – Does knockback make creepers explode
minecraft-java-edition
Related Solutions
After a significant amount of testing, of which GLaDOS would be proud, we managed to come up with a fairly simple table of data from which to formulate an answer.
Variation of about .5 blocks
To reach these results, I first enchanted my weapons until I had Knockback I and Knockback II (note: the minimum modified levels for these enchants are 5 and 25, respectively).
I then had my associate spawn Zombies in the Knockback Testing Super System™ so that I could attack the Zombies from a safe, secure location.
We first tested a Normal Sword (no enchantment) from a standing position, and then again while sprinting. We then repeated the process with enchanted swords. Once we reached a definitive conclusion, we moved on to testing with Bows and their related enchantments (in this case Punch). The results of our SCIENCE can be found at the top of this answer.
I hope this helped!
First note that the Enchanting page on the wiki says that Protection, Fire Protection, Blast Protection, and Projectile Protection are all mutually exclusive, but it looks like you can have Feather Falling on boots with one of the other enchantments.
The Armor page linked in the question has a table of "Enchantment Protection Factors" provided by each enchantment. I have duplicated the relevant parts of the table below:
Since increasing the level of the enchantment only increases the EPF, when trying to find the "best" protection it is only worth looking at the highest level enchantment. The article also says that in order to maximize protection from a particular kind of damage, you would need 25 points of protection for that damage type.
Since there are 3 different types of damage, one would need 75 effective points of protection, but since each armor can add either up to 11 points to one type of protection or 5 points to each type (which is like adding 15 total), the max is 60 effective points of protection. So, you can't max out everything. And plain Protection can't be maxed out at all. Therefore, the best armor depends on what you are looking for:
If you want to maximize the minimum protection value:
Put Protection IV on each piece of armor. This will give you 20 points in every type of protection. As a side bonus, if you put any level of Feather Falling on the boots, you will max out fall damage protection.
- Protection EPF: 20
- Fire EPF: 20
- Blast EPF: 20
- Projectile EPF: 20
- Feather Falling EPF: 38 (capped to 25)
If you want to maximize the average of protection values:
Again, put Protection IV on each piece of armor. Adding Protection IV to a piece of armor adds 5 to each protection type, so it adds 5 to the average. Adding any other protection enchantment adds at most 11/3<5 EPF on average.
- Protection EPF: 20
- Fire EPF: 20
- Blast EPF: 20
- Projectile EPF: 20
- Feather Falling EPF: 38 (capped to 25)
If you want to prioritize a particular protection type:
Plain old Protection:
Put Protection IV on all 4 pieces of armor.
- Protection EPF: 20
- Fire EPF: 20
- Blast EPF: 20
- Projectile EPF: 20
- Feather Falling EPF: 38 (capped to 25)
Projectile Protection then Blast Protection:
Put Projectile Protection IV on two pieces of armor, Blast Protection IV on one piece of armor, and Protection IV on the last piece of armor.
- Protection EPF: 5
- Fire EPF: 5
- Blast EPF: 16
- Projectile EPF: 27 (capped to 25)
- Feather Falling: 23
Projectile Protection, then Fire Protection:
Put Projectile Protection IV on two pieces of armor, Fire Protection IV on one piece of armor, and Protection IV on the last piece of armor.
- Protection EPF: 5
- Fire EPF: 14
- Blast EPF: 5
- Projectile EPF: 27 (capped to 25)
- Feather Falling: 23
Blast Protection then Projectile Protection:
Put Blast Protection IV on two pieces of armor, Projectile Protection IV on one piece of armor, and Protection IV on the last piece of armor.
- Protection EPF: 5
- Fire EPF: 5
- Blast EPF: 27 (capped to 25)
- Projectile EPF: 16
- Feather Falling: 23
Blast Protection then Fire Protection:
Put Blast Protection IV on two pieces of armor, Fire Protection IV on one piece of armor, and Protection IV on the last piece of armor.
- Protection EPF: 5
- Fire EPF: 14
- Blast EPF: 27 (capped to 25)
- Projectile EPF: 5
- Feather Falling: 23
Fire Protection, then the other two
Put Fire Protection IV on 2 pieces of armor and Protection IV on two pieces of armor.
- Protection EPF: 10
- Fire EPF: 28 (capped to 25)
- Blast EPF: 10
- Projectile EPF: 10
- Feather Falling: 28 (capped to 25)
Fire Protection then Projectile Protection:
Put Fire Protection IV on 3 pieces of armor and Projectile Protection IV on one piece of armor.
- Protection EPF: 10
- Fire EPF: 27 (capped to 25)
- Blast EPF: 0
- Projectile EPF: 11
- Feather Falling: 18
Fire Protection then Blast Protection:
Put Fire Protection IV on 3 pieces of armor and Blast Protection IV on one piece of armor.
- Protection EPF: 0
- Fire EPF: 27 (capped to 25)
- Blast EPF: 11
- Projectile EPF: 0
- Feather Falling: 18
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Best Answer
I've just tested with a creeper spawner and a sword with knockback. Knockback is not the cause of the explosion.
What I think is happening to you is that the creeper is reaching the creeper event horizon - beyond which it definitely will explode, then you're hitting it. It's ending up miles away - much further away than it would be normally - then exploding.