Higher: read and compare cumulative-frequency diagrams
Trace threshold and inverse readings, subtract cumulative estimates, and compare proportions on supplied guides with different sample totals.
Exam scope and assessment notes
The first six lessons are shared Foundation work inherited by Higher; the last four are additional Higher histograms and cumulative-frequency work. Construct actual labelled diagrams with their scales, units and keys. Unequal continuous intervals need frequency density and area; partial-class and straight-guide readings are estimates, and a flat inverse can be an interval. Numerical agreement does not award marks or establish mastery; written explanations need human review. Statistical measures and probability remain separate. Linear November 2026/June 2027 entries and regional-centre eligibility differ from modular awards. Publisher map/contents are navigation only: F6.1Aii is a modular subpart, not the whole linear F6.1A row. Book1 Handling Data3 map398–428 differs from proof397/summary426/next428; Book2 Handling Data6 map208–222 differs from proof207/summary221/next222. Relevant chapter and Hub bodies remain unavailable; specialist and formal-assessment approval remain pending.
Before you begin
- Construct cumulative diagrams and interpret their endpoint counts.
- Interpolate proportionally on a declared straight segment.
- Calculate percentages using the correct sample total.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
A complete sample has 100 observations. The cumulative readings at thresholds a and b are 31 and 76. What estimates a < x ≤ b?
What you will learn
- Read below, above and between thresholds using a supplied cumulative guide.
- Trace inverse cumulative-count readings and identify where they need not be unique.
- Use each sample’s own total for proportion comparisons and retain unrounded estimates until the final report.
Use the supplied cumulative-frequency guide through (0,0), (10,8), (20,24), (30,42), (50,60), with straight segments between the plotted points. The horizontal axis is the measurement x and the vertical axis Cumulative frequency. Estimate the counts at or below x=15 and x=40, the count with 15 < x ≤ 40, and the count above 40. Find the measurement corresponding to cumulative count 33. Show vertical/horizontal reading traces, interpolation and the required subtraction, distinguishing within-class estimates from exact grouped endpoints.
Choose your representation, enter its actual categories, counts, geometry and labels, and explicitly record it. No table margin, scale, missing sector, density, cumulative point or reading trace is filled for you.
Original supplied data
Only literal data are supplied. A missing entry is displayed as not supplied; requested totals, frequencies, angles, density calibration, cumulative constructions and read-off traces are not generated on this board.
All metric panels in this board share one camera and equal Cartesian drawing units. Equal full widths, heights and pie radii therefore stay visibly comparable; no individual panel is independently fitted. Histogram numerical frequency density is its entered vertical calibration. Tables and tally strokes are symbolic displays.
Supplied cumulative guide A
Supplied data only. This is a display state, not a correctness or marking result.
Blue is supplied geometry, amber is my actual work, purple is dirty retained work and green is a separately gated reference. Rendering never repairs a wrong count, overlap, radius, calibration, cumulative decrease or read-off elbow. Tool coordinates are bounded to±1000000; finite unsupported portions are not silently clamped. Up to1000 explicit pictogram pieces and100 tally bundles per displayed row are rendered. Screen size is not physical instrument calibration. Readiness and fixed numerical comparison do not mark reasoning, award marks, prove mastery or provide teacher/specialist/formal-assessment approval.
Observed and whole-class counts stay distinct from within-class histogram or cumulative-guide estimates. A zero-frequency plateau can give an interval of inverse readings. No median, quartile, midpoint-mean or probability teaching credit is supplied by this display.
My actual threshold-to-count trace at 15
No actual representation is recorded for this action.
The board places only the coordinates you explicitly choose into the selected slot. It generates no other corner, bar, sector or reading elbow. Interval-area bounds are two measurements, not a planar point.
My quantities, conclusions and explanation
Enter an exact fraction or finite decimal, with the precision and quantity unit explicitly requested in the question.
Enter an exact fraction or finite decimal, with the precision and quantity unit explicitly requested in the question.
Enter an exact fraction or finite decimal, with the precision and quantity unit explicitly requested in the question.
Enter an exact fraction or finite decimal, with the precision and quantity unit explicitly requested in the question.
Enter an exact fraction or finite decimal, with the precision and quantity unit explicitly requested in the question.
Enter an exact fraction or finite decimal, with the precision and quantity unit explicitly requested in the question.
Explain the actual construction and its conditions. Text presence does not establish a correct argument.
These original fixed cases support self-checking. They do not mark proofs or written explanations, award marks or mastery, certify instrument accuracy, or provide specialist or formal assessment approval. Within-class histogram and cumulative-guide readings are estimates, while supplied whole-class counts remain exact. A plateau may give an interval rather than one inverse reading.
Trace from a measurement to a count
On a cumulative-frequency diagram, move vertically from a measurement on the horizontal axis to the given guide, then horizontally to read its cumulative count. That value estimates the number at or below the measurement when the threshold lies inside a grouped class. At a supplied class boundary, the plotted count is an exact fact from the grouped table.
For the number with a < x ≤ b, subtract the cumulative reading at a from the reading at b. For the number above b, subtract its reading from the complete sample total. The supplied straight-segment guides in these tasks make the numerical readings reproducible; they still allocate grouped observations inside classes by an estimation guide rather than revealing their raw locations.
Reverse the reading and keep its limits
To find the measurement corresponding to a cumulative count, start at that count on the vertical axis, move horizontally to the guide and then vertically down to the measurement axis. Within one stated straight segment, proportional horizontal and vertical changes can support the graph reading. Draw the guide lines as well as recording the calculation, so the quantities being read remain visible.
If the guide is flat at the requested count, the inverse can be an interval rather than a single measurement. A grouped diagram also cannot justify extra decimal precision beyond its data and scale. Use the declared guide when checking numerical estimates, and keep the distinction between its computed position and an exactly observed raw threshold.
Compare whole samples and report estimates
When two cumulative guides represent different total sample sizes, compare proportions using each curve’s own final cumulative count. A larger count at one threshold may be a smaller share of the larger sample. Keep the curve key and totals visible, and say whether you are comparing numbers or percentages at the same measurement.
Retain unrounded readings while subtracting, then apply the requested rounding to the final estimated count. Rounding each intermediate value first can change an interval estimate. A fractional model count is not a fraction of a real individual; it expresses the grouped-guide estimate. These threshold and inverse tasks do not establish every statistical measure or any probability-model result.
Sources for this lesson
- Pearson Mathematics A linear specification · Issue 2 · Foundation printed 24 / physical 30; Higher printed 39 / physical 45; inheritance printed 27 / physical 33
- Pearson 2026/2027 entry manual · centre regions physical 3; Mathematics A physical 25
- Pearson second-edition modular book/Hub map · literal navigation only · physical 7, 9, 11
Pause and explain
At a common threshold, one guide has 30 of 50 observations below it and another has 40 of 80. Which has the greater proportion?
Worked example
Use the supplied cumulative-frequency guide through (0,0), (10,8), (20,24), (30,42), (50,60), with straight segments between the plotted points. The horizontal axis is the measurement x and the vertical axis Cumulative frequency. Estimate the counts at or below x=15 and x=40, the count with 15 < x ≤ 40, and the count above 40. Find the measurement corresponding to cumulative count 33. Show vertical/horizontal reading traces, interpolation and the required subtraction, distinguishing within-class estimates from exact grouped endpoints.
Show the worked solution
- Trace vertically from each threshold to the supplied guide, then horizontally to the count axis. The straight-segment readings are F(15)=8+(15−10)/(20−10)×(24−8)=16 and F(40)=42+(40−30)/(50−30)×(60−42)=51. These are within-class estimates, even if a value is an integer.
- Subtract cumulative readings for the interval: 51−16=35. Use the exact grouped total 60 for the upper tail: 60−51=9 estimated observations above 40.
- For cumulative count 33, trace horizontally to the guide and down to x. It lies between endpoint counts 24 and 42, so x=20+(33−24)/(42−24)×(30−20)=25 measurement units.
- Keep the supplied guide and visible reading traces. Endpoint counts come from the grouped data, while the intermediate threshold and inverse positions are estimates under the declared straight-segment guide; no extra raw precision is established.
Answer Guide estimates: F(15)=16, F(40)=51; 15 < x ≤ 40: 35; above 40: 9. The inverse reading at cumulative count 33 is x≈25 measurement units. Total 60.
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Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Use the supplied cumulative-frequency guide through (20,0), (30,12), (45,36), (65,66), (90,80), with straight segments between the plotted points. The horizontal axis is the measurement x and the vertical axis Cumulative frequency. Estimate the counts at or below x=40 and x=75, the count with 40 < x ≤ 75, and the count above 75. Find the measurement corresponding to cumulative count 54. Show vertical/horizontal reading traces, interpolation and the required subtraction, distinguishing within-class estimates from exact grouped endpoints. Report final estimated numbers of individuals to the nearest whole person, keeping unrounded working until after subtraction.
Give me a hint
Trace in the required direction first. Use a difference for an interval, total minus reading for an upper tail, and each sample’s own total for a share.
Compare my reasoning
- Trace vertically from each threshold to the supplied guide, then horizontally to the count axis. The straight-segment readings are F(40)=12+(40−30)/(45−30)×(36−12)=28 and F(75)=66+(75−65)/(90−65)×(80−66)=358/5. These are within-class estimates, even if a value is an integer.
- Subtract cumulative readings for the interval: 358/5−28=218/5. Use the exact grouped total 80 for the upper tail: 80−358/5=42/5 estimated observations above 75.
- For cumulative count 54, trace horizontally to the guide and down to x. It lies between endpoint counts 36 and 66, so x=45+(54−36)/(66−36)×(65−45)=57 measurement units.
- Retain F(40)=28 and F(75)=358/5=71.6 while subtracting: the interval estimate is 218/5=43.6 and the upper-tail estimate 42/5=8.4. Round only final requested counts: at/below the thresholds 28 and 72 people, between them 44, above 75 about 8; the inverse reading is x=57.
Guide estimates: F(40)=28, F(75)=358/5; 40 < x ≤ 75: 218/5; above 75: 42/5. The inverse reading at cumulative count 54 is x≈57 measurement units. Total 80. Final whole-person reports: 28 and 72 at/below the thresholds, 44 between, 8 above; retain 71.6, 43.6 and 8.4 in the unrounded working.
Look for these in your work
- Use the actual supplied guide and show threshold/inverse reading traces on labelled axes.
- Calculate the correct differences or proportions while retaining unrounded working.
- Distinguish exact grouped endpoints from model estimates and follow any final rounding requirement.
Two supplied cumulative-frequency guides use measurement boundaries 0, 10, 20, 40 and straight segments between endpoints. Group A has cumulative counts 0, 16, 48, 80; Group B has 0, 30, 66, 120. Keep a clear key and compare counts on a common measurement scale. Read the exact grouped counts at 20 and compare their percentages using the correct totals. Estimate each count with 10 < x ≤ 30, showing graph traces and subtraction. Also give A’s reading at 30 and estimated count above 30 as checks. Explain why 66 versus 48 alone does not compare proportions.
Give me a hint
Trace in the required direction first. Use a difference for an interval, total minus reading for an upper tail, and each sample’s own total for a share.
Compare my reasoning
- Keep both supplied guides and identify their exact final totals: A has 80 and B has 120. At the boundary x=20 their exact grouped cumulative counts are 48 and 66.
- Convert each to its own proportion: 48/80=3/5=60% for A and 66/120=11/20=55% for B. B has more observations at or below 20, but A has the larger proportion by 5 percentage points.
- Trace x=30 to each stated straight segment between 20 and 40. For A, F(30)=48+(10/20)×(80−48)=64. For B, F(30)=66+(10/20)×(120−66)=93. These within-class readings are estimates.
- At x=10 the given counts are 16 and 30. Subtract to estimate 10 < x ≤ 30: A gives 64−16=48, B gives 93−30=63. A’s estimated count above 30 is 80−64=16. Show the reading guides and explain that raw counts alone ignore the unequal totals.
At x=20: A=48 of 80=60%; B=66 of 120=55%. A has the greater proportion although B has the larger count. A’s estimated F(30)=64 and B’s F(30)=93. The estimates for 10 < x ≤ 30 are A=48 and B=63; A above 30 is estimated as 16. Counts at the supplied boundary 20 are exact grouped facts; readings inside a class use the stated guide.
Look for these in your work
- Use the actual supplied guide and show threshold/inverse reading traces on labelled axes.
- Calculate the correct differences or proportions while retaining unrounded working.
- Distinguish exact grouped endpoints from model estimates and follow any final rounding requirement.
Use the supplied cumulative-frequency guide through (-5,0), (0,10), (8,34), (20,58), (40,70), with straight segments between the plotted points. The horizontal axis is the measurement x and the vertical axis Cumulative frequency. Estimate the counts at or below x=12 and x=30, the count with 12 < x ≤ 30, and the count above 30. Find the measurement corresponding to cumulative count 46. Show vertical/horizontal reading traces, interpolation and the required subtraction, distinguishing within-class estimates from exact grouped endpoints.
Give me a hint
Trace in the required direction first. Use a difference for an interval, total minus reading for an upper tail, and each sample’s own total for a share.
Compare my reasoning
- Trace vertically from each threshold to the supplied guide, then horizontally to the count axis. The straight-segment readings are F(12)=34+(12−8)/(20−8)×(58−34)=42 and F(30)=58+(30−20)/(40−20)×(70−58)=64. These are within-class estimates, even if a value is an integer.
- Subtract cumulative readings for the interval: 64−42=22. Use the exact grouped total 70 for the upper tail: 70−64=6 estimated observations above 30.
- For cumulative count 46, trace horizontally to the guide and down to x. It lies between endpoint counts 34 and 58, so x=8+(46−34)/(58−34)×(20−8)=14 measurement units.
- Keep the supplied guide and visible reading traces. Endpoint counts come from the grouped data, while the intermediate threshold and inverse positions are estimates under the declared straight-segment guide; no extra raw precision is established.
Guide estimates: F(12)=42, F(30)=64; 12 < x ≤ 30: 22; above 30: 6. The inverse reading at cumulative count 46 is x≈14 measurement units. Total 70.
Look for these in your work
- Use the actual supplied guide and show threshold/inverse reading traces on labelled axes.
- Calculate the correct differences or proportions while retaining unrounded working.
- Distinguish exact grouped endpoints from model estimates and follow any final rounding requirement.
Common mistakes
- Using a cumulative reading directly as a between-threshold count without subtracting.
- Comparing raw cumulative counts as proportions when final totals differ.
- Rounding before subtraction or treating a plateau inverse as uniquely determined.
What can you explain now?
Why should cumulative estimates be subtracted before rounding a final estimated number of people?
Compare with the explanation
Early rounding can alter the difference. Keep the guide readings unrounded, subtract, and then round the requested final estimate.
The final rounding rule applies to the estimated interval count, not independently to every intermediate reading.
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Make it stick
Describe the two directions of graph reading, the subtractions for intervals and upper tails, and the fair comparison of unequal-sized samples.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.