IGCSE›Edexcel IGCSE Maths›Mind mapsCumulative Frequency DiagramsEdexcel IGCSE Maths: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsWhat is it?Cumulative frequency is a running totalAdd each frequency to all the previous onesLast value equals the total frequencyDrawing the curvePlot against the upper bound, not midpointStart at the first lower bound, frequency 0Join with a smooth S-curve (ogive)Curve never goes downReading quartilesQ1Q_1Q1 at n4\frac{n}{4}4nMedian at n2\frac{n}{2}2nQ3Q_3Q3 at 3n4\frac{3n}{4}43nGo across to the curve, then downIQR=Q3−Q1IQR = Q_3 - Q_1IQR=Q3−Q1Cumulative freqcurves and box plotsQ1Q_1Q1Q2Q_2Q2Q3Q_3Q3Box plotsFive values: min, Q1Q_1Q1, median, Q3Q_3Q3, maxBox from Q1Q_1Q1 to Q3Q_3Q3, line at medianWhiskers go to min and maxDraw to scale with a rulerComparingCompare the median (location)Compare the IQR (spread)Both must be in contextSmaller IQR → more consistentExam tipsNever plot against the midpointUse n2\frac{n}{2}2n, not n+12\frac{n+1}{2}2n+1, on the graphSketch the curve lightly in pencil firstGraph readings are estimates