IB›IB Maths: Analysis and Approaches HL›Mind maps4.2 Presentation of dataIB Maths: Analysis and Approaches HL: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsFrequency tablesClasses as inequalities, no gaps or overlaps10≤L<1510 \le L < 1510≤L<15, then 15≤L<2015 \le L < 2015≤L<2015 cm goes in the upper classGrouped data gives estimates onlyHistogramsTouching bars, heights are frequenciesEqual class widths hereShows shape: clusters, skew, gapsNo gaps because data are continuousCumulative frequencyMedian at n2\frac{n}{2}2nQ1Q_1Q1 at n4\frac{n}{4}4n, Q3Q_3Q3 at 3n4\frac{3n}{4}43npppth percentile at p100×n\frac{p}{100} \times n100p×nIQR =Q3−Q1= Q_3 - Q_1=Q3−Q1Interpolate: a+rf×wa + \frac{r}{f} \times wa+fr×wData displaypresentation of dataQ1Q_1Q1Q3Q_3Q3IQRBox and whiskerFive-number summary: min, Q1Q_1Q1, median, Q3Q_3Q3, maxOutlier: beyond 1.5×IQR1.5 \times \text{IQR}1.5×IQR from a quartileWhisker stops at the last non-outlierQ1=95Q_1 = 95Q1=95, Q3=145Q_3 = 145Q3=145: outlier above 220Comparing dataCompare one centre and one spreadInterpret each in contextMedian near Q1Q_1Q1: positively skewedMedian near Q3Q_3Q3: negatively skewedSymmetric: may be normalExam tipsNot 101010–151515, 161616–202020 for continuous dataUse n2\frac{n}{2}2n, not n+12\frac{n+1}{2}2n+1, for grouped dataPlot cumulative frequency at the upper boundaryUse IQR not range when outliers existNever compare numbers without context