How many outcomes are there to a shower?
    
    We have to set our scope and threshold. You're probably
    thinking that there is one outcome: getting clean.
    However, there are infinite outcomes to any event if
    you're not careful.
    
    First, I will limit the observation to the instant the
    shower is done. What if I don't? If you count the process,
    then every footstep you take in the shower will impact
    how the shower goes on a microscopic level that, with 
    just the right chance, might snowball into a visible effect,
    like slipping and injuring yourself. I will not count footsteps.
    I will not count the way your muscles contract and relax unless
    they are a factor in the success of the shower. Therefore,
    I will assume the shower is successful; that is, complete.
    
    Second, I will limit the impact of the shower to external
    physical cleanliness. I will not count psychological effects,
    nor will I count the effect (if any) it has on the movement
    of red blood cells inside of you, whether they hit the walls
    of your vessels in certain ways as they squeeze through, nor will
    I pretend that such movement affects the process of showering.
    If I count it, there will be infinite outcomes, most of which have
    no real discernible value, because the useful data is cleanliness.
    I will assume that the way soap bubbles on your skin has no impact,
    because there are infinite manners in which the bubbles will appear,
    if they appear at all in the foam. I will count, however, whether
    the soap covers every picometer of your skin. If not, then how much
    of the skin it touches. This is important in assessing the totality
    of the cleansing.
    
    With that out of the way, because there are infinite numbers, there
    are infinite "levels" of cleanliness. The percentage can be any number
    between 0 and 100. However, some people don't use soap or shampoo
    at all. Sometimes, people have a quick shower to rinse off sweat and
    nothing else. In cases like this, and in all cases really, it may be
    more useful to measure the change in cleanliness level. In other
    words, we will count how much cleaner you got. This should exclude
    obvious extreme cases like not turning on the water. A shower must
    constitute of water at the very least, and the water must touch you.
    Usage of soap is not a must, but another factor in cleanliness.
    A shower using a bit of soap cleans more than a shower without any.
    That translates meaningfully into the calculation and measurement.
    
    To reduce the number of outcomes from infinite to usable, we can
    define ranges and conditions. For example, we can produce a binary
    of "clean" and "not clean" based on a threshold of cleanliness. If your
    cleanliness at the end of the shower is above a certain percentage, you
    are clean. An issue with this is that you may have been clean before the
    shower too, so this does not show the effect of the shower. We can thus
    return to the change-measuring method: a shower is effective if its
    net cleanliness change meets the amount required by the showerer. This
    gives room for relative usefulness of the shower. Someone entering the
    shower might not be looking for the deepest cleanse. I disagree with
    that personally, but that does not matter.