Discrete frequency tables and repeated positions
Use frequencies as repeated observations, calculate weighted totals, and locate actual median positions without losing zero rows or modal ties.
Exam scope and assessment notes
The first four lessons are shared Foundation work inherited by Higher; the last four are additional Higher spread, quartile and cumulative-frequency reading work. Keep the actual repeated observations and frequencies, state units, and distinguish an average from spread. Grouped midpoint means and within-class graph readings are estimates. The chosen discrete quartile rule is median of each half, excluding the overall middle observation when the count is odd; it is not claimed as a universal Pearson algorithm. Draw the horizontal and vertical guides yourself, use each graph’s own total, and retain a full plateau interval when an inverse is not unique. Fixed numerical agreement does not mark reasoning or award marks or mastery. Specialist and formal-assessment approval remain pending. This is the Issue 2 linear 4MA1 scope: November 2026/June 2027 entries and regional-centre eligibility differ from modular awards. Literal second-edition Book2 Handling Data4/5/6 and Hub tags guide navigation only; no Book1 6.2 tag or verified chapter/Hub body is inferred. Handling Data6 map208–222 conflicts with proof chapter207/summary221/next222; Handling Data4 map39–60 extends beyond summary59 before next61. Graphical representation6.1 and probability6.3 remain separate.
Before you begin
- Calculate summaries from a complete list.
- Multiply signed values by whole-number frequencies.
- Track ordered positions and cumulative counts.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
A table has values 1 and 3 with frequencies 2 and 4. How many observations are represented?
What you will learn
- Interpret each frequency as a count of repeated values.
- Calculate weighted means and locate medians through cumulative positions.
- Handle zero-frequency extremes, ties and unobserved medians correctly.
A discrete table gives values [0, 1, 2, 3, 4] with corresponding frequencies [2, 5, 6, 3, 0], in books. Find the number of observations, mean, median, every mode and range. Explain how the frequencies determine the median and any zero rows or ties.
Enter your own actual observations, positions, products, operations and guide endpoints. No count, total, role, result, quartile, graph height, unit or precision is filled for you. Recording is an attempt, not a correctness result.
Original supplied observations and tables
| Supplied value | Supplied frequency |
|---|---|
| 0 | 2 |
| 1 | 5 |
| 2 | 6 |
| 3 | 3 |
| 4 | 0 |
Original rows only. No total, product, cumulative count, midpoint or summary is inserted.
Only literal observations, frequencies, intervals and supplied cumulative guides are shown initially. The display does not sort observations, compute a total, average, quartile, rank or recovered value, or prefill a learner operation.
Blue denotes literal supplied guides, amber actual entered work, purple dirty retained work, and green a separately gated reference. Wrong and partial values are never repaired. The drawing bound is±1,000,000 coordinates, with at most512 scalar entries and128 cumulative points; these are tool bounds, not mathematical laws. Native clipping does not clamp values. No completed target is silently substituted.
The selected median-of-halves convention excludes the overall middle observation for odd lists. Grouped means and guide read-offs remain estimates. A zero-frequency plateau can give an interval rather than a unique reading. Fixed guide comparisons use the separate canonical700×500 policy with each source total; the tolerance is not a current-screen pixel or official marking tolerance. Text presence, operation consistency and numerical self-check do not approve reasoning, statistical claims, marks, mastery, teacher/specialist or formal assessment. No probability or new boxplot teaching credit is granted.
Record weighted products, cumulative positions, modal rows and observed extreme rows
Row indices start at 0 for the first supplied row. Middle observation positions start at 1 and count repetitions, rather than table rows.
No actual work is recorded for this action.
Choose an explicit mode statement.
This is symbolic or one-dimensional work. These controls do not turn observation positions, row indices, extremes or interval boundaries into Cartesian points.
My quantities, conclusions and explanation
For a numerical list, use comma-separated values with no brackets or one balanced enclosing pair, or type none when you mean no mode. State the actual unit and exact, estimate or one-decimal-place precision yourself.
Retain the stated data, units, signs and precision. Numerical agreement is a self-check only.
Retain the stated data, units, signs and precision. Numerical agreement is a self-check only.
Retain the stated data, units, signs and precision. Numerical agreement is a self-check only.
Retain the stated data, units, signs and precision. Numerical agreement is a self-check only.
Retain the stated data, units, signs and precision. Numerical agreement is a self-check only.
Retain the stated data, units, signs and precision. Numerical agreement is a self-check only.
Retain the stated data, units, signs and precision. Numerical agreement is a self-check only.
A written attempt needs actual reasoning; text presence does not approve the argument.
A written attempt needs actual reasoning; text presence does not approve the argument.
These are original fixed cases for self-checking, not automatic marking, mastery or teacher/specialist/formal-assessment approval. The stated median-of-halves convention is a chosen convention. Grouped midpoint means and within-class CF readings remain estimates; a plateau can give a full interval. A physical instrument and calibrated graph are separate from the screen. No probability credit follows.
A row is not one observation
A discrete frequency table compresses a repeated list. The value column tells you the recorded value, and the frequency column tells you how many observations have that value. Add the frequencies to find the number of observations. The number of printed rows is usually a different quantity and is not the denominator for the mean.
A row with frequency zero is still useful information about the stated category, but it contributes no observations. It contributes nothing to the total and cannot supply an observed minimum or maximum. Check that frequencies are nonnegative whole counts and that every required frequency is known; a blank cell is not automatically a zero. If the total frequency is zero, there is no observed distribution from which to invent a mean, median or range.
Calculate using counts and positions
Make a product column containing value × frequency. Adding that column gives the total of the full repeated data, so the mean is the product-column total divided by the total frequency. This gives each observation equal weight even when some row values are much more common than others.
For the median, find the middle observation position or positions using the total frequency, then build cumulative counts down the ordered rows. A row occupies all positions after the previous cumulative total up to its own cumulative total. For an even count, locate both central observations before averaging their values; do not average their position numbers.
Modes, extremes and interpretation
A modal value is a row value with greatest frequency. If more than one repeated value shares the greatest frequency, give each mode rather than choosing the first row. If no value repeats, use the stated no-mode convention. Find the range from the largest and smallest values that actually have positive frequencies.
A median can be a value with zero frequency if the two middle observations lie on either side of it. That does not insert a new observation into the table. Your explanation should show the two actual middle observations and the averaging step. Check that the final mean and median remain within the observed extremes, while keeping their original data unit.
Sources for this lesson
- Pearson Mathematics A linear specification · Issue 2 · Foundation printed24/physical30; Higher printed39/physical45; inheritance printed27/physical33
- Pearson 2026/2027 entry manual · centre regions physical3; Mathematics A physical25
- Pearson second-edition modular book/Hub map · literal navigation only · physical9,10,11
Pause and explain
A discrete table has rows value 6 with frequency 0, value 9 with frequency 3, and value 12 with frequency 2. Which values determine its range?
Worked example
A discrete table gives values [0, 1, 2, 3, 4] with corresponding frequencies [2, 5, 6, 3, 0], in books. Find the number of observations, mean, median, every mode and range. Explain how the frequencies determine the median and any zero rows or ties.
Show the worked solution
- Sum the frequencies to get 16 observations, not 5. Sum value × frequency to get 26 books.
- Mean = 26/16 = 13/8 books. Locate positions 8 and 9 in cumulative counts; median = 2 books.
- Mode(s): 2 books; range = 3 books. The unused 4-books row has frequency zero, so the observed maximum is 3 books.
Answer Number of observations = 16; weighted total = 26. Mean = 1.625, median = 2, mode = 2, range = 3, in books.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
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.
A discrete table gives values [1, 2, 3, 4] with corresponding frequencies [3, 4, 2, 1], in goals. Find the number of observations, mean, median, every mode and range. Explain how the frequencies determine the median and any zero rows or ties.
Give me a hint
Sum frequencies and build cumulative counts before locating the middle pair.
Compare my reasoning
- Sum the frequencies to get 10 observations, not 4. Sum value × frequency to get 21 goals.
- Mean = 21/10 = 21/10 goals. Locate positions 5 and 6 in cumulative counts; median = 2 goals.
- Mode(s): 2 goals; range = 3 goals. Positions 4 through 7 are all 2 goals, so both central positions are 2.
Number of observations = 10; weighted total = 21. Mean = 2.1, median = 2, mode = 2, range = 3, in goals.
Look for these in your work
- Use the total frequency as denominator.
- Identify actual central observation positions.
- Handle zero-frequency rows and all modal ties.
A discrete table gives values [-2, 0, 2, 4] with corresponding frequencies [2, 5, 1, 4], in points. Find the number of observations, mean, median, every mode and range. Explain how the frequencies determine the median and any zero rows or ties.
Give me a hint
Keep the zero value distinct from a zero frequency; they mean different things.
Compare my reasoning
- Sum the frequencies to get 12 observations, not 4. Sum value × frequency to get 14 points.
- Mean = 14/12 = 7/6 points. Locate positions 6 and 7 in cumulative counts; median = 0 points.
- Mode(s): 0 points; range = 6 points. The central positions both lie in the zero-points row; a zero value is not a missing observation.
Number of observations = 12; weighted total = 14. Mean = 7/6, median = 0, mode = 0, range = 6, in points.
Look for these in your work
- Use the total frequency as denominator.
- Identify actual central observation positions.
- Handle zero-frequency rows and all modal ties.
A discrete table gives values [0, 1, 2, 3, 4] with corresponding frequencies [1, 3, 0, 3, 1], in visits. Find the number of observations, mean, median, every mode and range. Explain how the frequencies determine the median and any zero rows or ties.
Give me a hint
Locate the two central observations and retain every tied greatest-frequency value.
Compare my reasoning
- Sum the frequencies to get 8 observations, not 5. Sum value × frequency to get 16 visits.
- Mean = 16/8 = 2 visits. Locate positions 4 and 5 in cumulative counts; median = 2 visits.
- Mode(s): 1, 3 visits; range = 4 visits. The central observations are 1 and 3, giving median 2 although no observation is 2; both 1 and 3 are modes.
Number of observations = 8; weighted total = 16. Mean = 2, median = 2, modes = 1, 3, range = 4, in visits. The median averages the central 1 and 3 to give 2, despite its zero frequency; both 1 and 3 are modes.
Look for these in your work
- Use the total frequency as denominator.
- Identify actual central observation positions.
- Handle zero-frequency rows and all modal ties.
Common mistakes
- Dividing the product sum by the row count.
- Using a zero-frequency value as an observed extreme.
- Choosing a mode by its numerical size rather than by frequency.
What can you explain now?
Why can a zero-frequency row be retained in a table without affecting its mean or median positions?
Compare with the explanation
It represents no observations, so it adds zero to both the count and the weighted total and occupies no ordered position.
Keeping the labelled row records an absent category; it does not create a value in the observed list.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Describe how to turn value/frequency rows into a count, weighted total, median-position intervals, modes and observed extremes.
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.