This was a question in a test: Do you have any figures showing the _______ of left-handedness in the general population?
Two of the answers were "occurrence" and "incidence". "incidence" was the answer, but I don't see why occurrence is not acceptable here.
EDIT: This was a language test, and only one answer was acceptable.
Incidence refers to the rate of occurrence, not an instance of occurrence (which is more synonymous with "incident"):
- The rate or extent of occurrence or effect: a high incidence of malaria in the tropics.
The following usage note may also be helpful:
These nouns refer to something that takes place or comes to pass:
Occurrence and happening are the most general: an everyday occurrence; a happening of no great importance.
Event usually signifies a notable occurrence: world events reported on the evening news; "Great events make me quiet and calm; it is only trifles that irritate my nerves" (Victoria).
Incident may apply to a minor occurrence: an incident that was blown out of proportion in the press.
The term may also refer to a distinct event of sharp identity and significance: an incident that changed scientists' understanding of the phenomenon.
An episode is an incident in the course of a progression or within a larger sequence: "Happiness was but the occasional episode in a general drama of pain" (Thomas Hardy).
-The Free Dictionary
The two words are generally synonymous in scientific usage. I am aware of a very slight difference, in that occurrence may mean the fact of something happening, as well as meaning the frequency of its occurrence. But such distinction is trivial, may not be agreed by other commentators, and does not justify saying that "occurrence" is an unacceptable answer. Unless the test related to a very specific course of study with clear and prior definition of terms, I feel the examiners were straining at subtleties that do not exist in general usage.
In my personal experience I'm used to incidence used more to describe binary relations - "A is incident upon B", "A is incident in B" - and occurrence being in the constant of some large and sort-of-inspecific space.
So, in your case: "occurrence of left-handedness".
From a mathematical perspective,
In an entity-event-state model,
For preamble, let us say that the set Marine Vessel, besides having many other members, has the following members
Submarine is a class of Marine Vessel. Warship is a class of Marine Vessel. Destroyer warship is a class of Warship.
The Delhi is a class of Destroyer warship. The Delhi class itself is not an existence of a ship, but a design of a class of warships. There are three instances of The Delhi in the Indian Navy.
The INS Mumbai is the occurrence of the state of existence (or an instance) of the The Delhi class.
Regardless that efforts to bring about its state of existence had encountered many stochastic events, the occurrence of the state of existence of INS Mumbai was not unexpected.
For normal human existence within the local frame of reference, INS Mumbai is a non-stochastic occurrence of state, not an incident state of existence of The Delhi class. (Whereas, a time traveler across a multiverse might call the INS Mumbai an incident, or an occurrence within an incident universe.)
Whereas, for the process engineers in Palo Alto intending to produce a batch of 3GHz CPU, but received the good news from their Penang, Malaysia testing facility that 15% of those CPUs had passed 3.5GHz tests. They celebrated the good news of that incident existence of 3.5 GHz CPUs, no doubt there had merely intended to be occurrences of 3.0GHz CPUs.
The Delhi class is designed/intended to handle many types of encounters. But it is specifically intended to destroy threats with guided missiles.
Type of Encounters is the set of events The Delhi class is expected to handle. Among other members, let us presume these are some of such eventual types of encounters
Let us say, that the INS Mumbai (being an occurrence of existence of The Delhi class) encountered an occurrence of the Somalian pirate vessel Dakari.
The occurrences of existence of INS Mumbai and the pirate vessel Dakari themselves were non-incident, but the encounter of the two vessels is an incident.
From the perspective of INS Mumbai, the encounter with Dakari was an instance of the event type pirate vessel encounters.
From the perspective of the Dakari, the encounter with INS Mumbai is probably an instance of which Somalian pirates might colloquially classify as event type when-outgunned-jump-overboard-and-swim-ashore.
Same incidence of an event, but classified differently by the INS Mumbai and the Dakari.
We can no doubt classify the incident of the encounter as an occurrence of an instance of {INS Mumbai->events->pirate vessel encounters}. However, being an event, especially with stochastic expectation of the event, it is more specifically an incident.
