GCSE›Edexcel GCSE Maths›Mind mapsBasic ProbabilityEdexcel GCSE Maths: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsThe scale0 = impossible, 1 = certain0.5 is an even chanceWrite as fraction, decimal or percentageNever negative or above 1Equally likelyP=favourabletotalP = \frac{\text{favourable}}{\text{total}}P=totalfavourableAssumes a fair coin or dieP(rolling a 6) =16= \frac{1}{6}=61Expected numberExpected = probability × n60 rolls: 16×60=10\frac{1}{6} \times 60 = 1061×60=10 sixesProbabilitythe basics00.51Relative frequencyExperimental: successes ÷ trialsOnly an estimate of true probabilityMore trials → closer to theoretical47 heads in 100 flips = 0.47Sum to 1Exhaustive outcomes add to 1P(not A)=1−P(A)P(\text{not } A) = 1 - P(A)P(not A)=1−P(A)Mutually exclusive: cannot happen togetherP(rain) 0.3 → P(no rain) 0.7Exam tipsAnswer of 1.2 or −0.3 is always wrongTwo-way tables: pick the correct totalTwo-way tables list outcomes systematically