Quartiles, percentiles and measures of dispersion

Worked examples (9)

• 1Quartiles of a small data set
• 2Ordering the data before anything else
• 3Quartiles of an ungrouped frequency distribution
• 4When the quartile position is not a whole number
• 5Quartiles when the last class is open-ended
• 6Estimating the quartiles from a cumulative frequency curve
• 7Estimating the IQR by linear interpolation
• 8When the quartile position lands exactly on a class boundary
• 9Why an extreme value cannot move the interquartile range

Model answers (9)

• ✓Model answer — 0479 Paper 1 style — 5.1
• ✓Model answer — 0479 Paper 1 style — 5.1
• ✓Model answer — 0479 Paper 1 style — 5.4
• ✓Model answer — 0479 Paper 2 style — 5.1, 5.4
• ✓Model answer — 0479 specimen Paper 1 Q5(d)(i) — 5.1
• ✓Model answer — 0479 Paper 1 style — 5.5
• ✓Model answer — 0479 specimen Paper 2 Q8(b) style — 5.5
• ✓Model answer — 0479 specimen Paper 1 Q5 — 5.4, 5.7
• ✓Model answer — 0479 Paper 1 style — 5.4, 5.7 (AO2)

Worked examples (9)

• 1Finding the position of a percentile
• 2Estimating a percentile from a cumulative frequency curve
• 3Recognising the quartiles as percentiles
• 4Estimating a percentile by linear interpolation
• 5The specimen's median by linear interpolation
• 6Finding the percentile corresponding to a given value
• 7Estimating frequencies in parts of the distribution
• 8A grade boundary set by a percentile
• 9How many fall between two percentiles

Model answers (9)

• ✓Model answer — 0479 Paper 1 style — 5.2
• ✓Model answer — 0479 Paper 1 style — 5.2
• ✓Model answer — 0479 Paper 2 style — 5.2
• ✓Model answer — 0479 Paper 2 style — 5.2
• ✓Model answer — 0479 specimen Paper 2 Q8(b) — 5.2
• ✓Model answer — 0479 specimen Paper 2 Q8(a) style — 5.2
• ✓Model answer — 0479 Paper 1 style — 5.2
• ✓Model answer — 0479 Paper 2 style — 5.2
• ✓Model answer — 0479 Paper 2 style — 5.2 (AO2)

Worked examples (9)

• 1The specimen's five bottles
• 2The same answer from both formulas
• 3Standard deviation of five test marks
• 4Standard deviation of an ungrouped frequency distribution
• 5Estimating the standard deviation of a grouped distribution
• 6Midpoints when the classes have gaps
• 7Working from Σx and Σx² alone
• 8A missing value, then the standard deviation
• 9Interpreting a small standard deviation

Model answers (9)

• ✓Model answer — 0479 Paper 1 style — 5.6
• ✓Model answer — 0479 Paper 1 style — 5.6
• ✓Model answer — 0479 specimen Paper 1 Q3(a) — 5.6
• ✓Model answer — 0479 Paper 2 style — 5.6
• ✓Model answer — 0479 specimen Paper 2 Q5(a) style — 5.6
• ✓Model answer — 0479 Paper 1 style — 5.6
• ✓Model answer — 0479 Paper 2 style — 5.6
• ✓Model answer — 0479 Paper 2 style — 5.6
• ✓Model answer — 0479 specimen Paper 1 Q3(b) — 5.6

Worked examples (9)

• 1The range of a small data set
• 2The range of an ungrouped frequency distribution
• 3One advantage and one disadvantage of the range
• 4Which measure can be found when a class is open-ended
• 5The effect of an extreme value on all three measures
• 6Choosing a measure for strongly skewed data
• 7Which of five measures survive one awkward table
• 8When the standard deviation is the right choice
• 9Matching the measure to the context

Model answers (9)

• ✓Model answer — 0479 Paper 1 style — 5.3
• ✓Model answer — 0479 Paper 2 style — 5.3
• ✓Model answer — 0479 Paper 1 style — 5.7
• ✓Model answer — 0479 specimen Paper 1 Q5(a), (b) — 5.7
• ✓Model answer — 0479 Paper 1 style — 5.7
• ✓Model answer — 0479 Paper 1 style — 5.7
• ✓Model answer — 0479 Paper 2 style — 5.7 (AO2)
• ✓Model answer — 0479 specimen Paper 1 Q3(b) style — 5.7 (AO2)
• ✓Model answer — 0479 Paper 2 style — 5.7 (AO2)