GCSE›Edexcel GCSE Maths›Mind mapsData Collection and SamplingEdexcel GCSE Maths: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsSamplesPopulation = whole group studiedSample = smaller group chosen from itLarger, representative samples are more reliableUnrepresentative sample gives biasLarge but biased samples still misleadCategorical dataFrequency table: each category and its countBar chart: equal widths, gaps between barsPictogram needs a keyPie angle =ftotal×360°= \frac{f}{\text{total}} \times 360°=totalf×360°45 of 180 chose blue → 90°Time seriesTime on the horizontal axisPoints joined by straight linesUsed to spot trendsTrend: upward, downward or repeatingData & samplingcollecting and displayingnfStem and leafStem = leading digit, leaf = final digitKeeps every original valueLeaves in ascending orderBack-to-back compares two data setsChoosing a diagramCategorical → bar chart, pie chart, pictogramSmall discrete → stem-and-leafOver time → time seriesComparing two sets → back-to-backExam tipsAlways include a key, e.g. 3 | 4 means 34Wrong diagram can misleadShow pie angle working