How do you calculate probability?
Kurze Antwort
Probability = number of favourable outcomes ÷ total number of equally likely outcomes. It is always between 0 (impossible) and 1 (certain), and can be written as a fraction, decimal or percentage. The probability of an event not happening is 1 minus the probability that it happens.
Schritt für Schritt
- Count all the possible outcomes, making sure they are equally likely.
- Count the outcomes you want.
- Divide the outcomes you want by the total and simplify.
- For two independent events both happening, multiply their probabilities.
- For either of two outcomes that cannot happen together, add their probabilities.
Beispiel
A bag has 3 red, 5 blue and 2 green counters. One is taken at random.
- Total: 3 + 5 + 2 = 10
- P(blue) = 5/10 = 1/2
- P(not green) = 1 − 2/10 = 8/10 = 4/5
Typische Fehler
- Giving a probability greater than 1.
- Forgetting to reduce the total when an item is not replaced.
- Adding probabilities when both events must happen. Use multiplication for and.
Einzelunterricht ist der schnellste Weg, Lücken vor einer Prüfung zu schließen. Die erste Stunde ist kostenlos.
Lehrkraft für Mathe finden