Explore what probability means and why it's useful.
Sannsynlighet handler bare å hvor stor sjanse det er for at en bestemt hendelse skal forekomme.
Whenever we’re unsure about the outcome of an event, we can talk about the probabilities of certain outcomes—how likely they are. The analysis of events governed by probability is called statistics.
Det beste eksemplet for forstå sannsynlighet er å kaste en mynt:
There are two possible outcomes—heads or tails.
Hva er sannsynligheten for at mynten lander på Krone? We can find out using the equation P(H)=? P(H) = ? .You might intuitively know that the likelihood is half/half, or 50%. Hvordan kan vi regne ut dette? Sannsynlighet =
I dette tilfellet:
Probability of an event = (# of ways it can happen) / (total number of outcomes)
P(A) = (# måter A kan skje) / (Det totale antall muligheter)
Eksempel 1
There are six different outcomes.
What’s the probability of rolling a one?
What’s the probability of rolling a one or a six?
Dersom vi bruker formelen ovenfor:
What’s the probability of rolling an even number (i.e., rolling a two, four or a six)?
Tips
  • The probability of an event can only be between 0 and 1 and can also be written as a percentage.
  • The probability of event A A is often written as P(A) P(A) .
  • If P(A)>P(B) P(A) > P(B) , then event A A has a higher chance of occurring than event B B .
  • If P(A)=P(B) P(A) = P(B) , then events A A and B B  are equally likely to occur.
Neste trinn:
Practice basic probability skills on Khan Academy —try our stack of practice questions with useful hints and answers!