Is your glass half full or half empty? Or are you in the possession of a receptacle that is utilized to fifty percent of its rated capacity.
If you are adding liquid to a container, when you reach fifty percent of the rated capacity, the said container is considered half full.
If reducing the quantity of liquid in a container, when you reach fifty percent of the rated capacity of that container, the container is considered half empty.
If a glass while static, is found to contain fifty percent of total capacity. It can reasonably be considered either half full or half empty without drawing any conclusions as to the mental state of the owner of the glass.
Depending on the circumstances relating to the desired state of the glass, the custodian of the glass may have certain emotive feelings relating to the condition of the glass.
For example: 1. The operator of a domestic dish washer, may upon opening the door of the dish washes, discovers that one renegade item of crystal wear has up turned and is half full with rinse water. This is an undesirable result that has been known to trigger an emotive reaction.
2. A thirsty athlete will be delighted to discover that an additional 50% of the sought after water is still remaining in his half empty cup. This is a desirable condition.
If considering and reporting the current capacity of a glass of water were a mathematical problem and not a thoughtful insight into the mental wellbeing of the owner of the glass, it would be this simple. You round up. 0-49% is empty. 50-100% is full. A glass at half capacity would always be half full.
Exhaustive scientific tests have proven in repeated studies that the amount of water in a half empty glass equals that of a half full glass. The mental state of the owner of the glass has no measurable influence on the quantity of water. However owners of half full glasses were found to be considerably more disappointed when they discovered they had no more water than the other glass owners. Conversely, owners of half empty glasses were delighted with the study results.