How long is a piece of string ? Could it be the right length ?
I have a piece of string. It is 9 feet 11 and a quarter inches long.
Just as a dead clock is right 2 times every 24 hours, how often will my piece of string be the right length ? Will that value change if I stretch the same piece of string a bit longer ?
If I shorten it with undoable knots, does that double the probability of it being the right length ?
I'm getting into a knot over this.

Hi notbeold I have given this some thought and I recon the undoable knots would lessen the probability of the aforesaid piece of shring being the right length. my reasoning runs thus.
the use to use to which the string is put necessitates that the string must be equal to or greater than the minimum effective requirement. instead of knots I would suggest cutting it into string ets.thus multiplying the potential uses. I hope this helps.

Could it be that you are just trying to "string" us along.. Does writing this mean I fell for it?..

Maybe he's trying to tie us up in knots

A piece of string that is 9 feet, 11 and a quarter inches long and tied into undoable knots is still a piece of string 9 feet, 11 and a quarter inches long.
The string's length didn't change.
It just has a different shape.

Each change of shape would have to effect the probability of it being optimally useful for the next job, or a selection of possible future uses.

Different species of probability may be influencing/influenced at different rates per different shape resulting from knotting, eg:
Murphy's Law would reduce probability of usefulness, especially as the string gets shorter, or more ungainly due to its knots;
The law of diminishing returns comes into effect with over use and wear and tear making it less useful in any length over time.

And what if the apparent knotted string is not embedded in standard cartesian 3D space as we see it, but is in fact in a twisted unique space, and is actually straight. In which case its usefulness may be compromised, and probabilities un-calculable.

Imagine if I had two pieces of string ! What is the probability of that ?

Tying a knot in a string doesn't make it shorter.
The string length is the same, unless you cut it.

Pull your shoelace out, measure it, put it back in and tie it.
Untie it and pull it back out, measure it...same.

If you tie a string's ends together is it still a string or is it a loop?