Secondary 3 G2 Mathematics Tutor Bukit Timah | Mean from Grouped Frequency Tables. Did you know? The mean from grouped intervals is usually an estimate.
This Secondary 3 G2 Mathematics tutor guide for Bukit Timah families explains mean from grouped frequency tables with worked examples, quick checks and independent practice. Use the student’s school chapter list to match the current learning sequence.
Frequency table
For values 2,3,4 with frequencies 1,2,1, the exact mean is (2×1+3×2+4×1)/4=3.
A helpful tutoring exercise changes the given values and asks the student to explain the method without copying the original worked solution. Identify the first incorrect decision before correcting arithmetic.
Class midpoint
For an interval from 0 to under 10, midpoint is 5. For 10 to under 20, midpoint is 15.
A helpful tutoring exercise changes the given values and asks the student to explain the method without copying the original worked solution. Identify the first incorrect decision before correcting arithmetic.
Grouped example
Suppose frequencies for intervals 0–10, 10–20, 20–30 are 2,3,1. Midpoints are 5,15,25.
A helpful tutoring exercise changes the given values and asks the student to explain the method without copying the original worked solution. Identify the first incorrect decision before correcting arithmetic.
Estimated mean
Multiply midpoint by frequency: 2×5+3×15+1×25=80. Divide by total frequency 6 to get approximately 13.3.
A helpful tutoring exercise changes the given values and asks the student to explain the method without copying the original worked solution. Identify the first incorrect decision before correcting arithmetic.
Why an estimate
The exact original observations inside each interval are unknown. Midpoints are representative assumptions.
A helpful tutoring exercise changes the given values and asks the student to explain the method without copying the original worked solution. Identify the first incorrect decision before correcting arithmetic.
Checking
The total frequency is 2+3+1=6, not three classes. The estimated mean should lie between the lowest and highest class values.
A helpful tutoring exercise changes the given values and asks the student to explain the method without copying the original worked solution. Identify the first incorrect decision before correcting arithmetic.
Practice
For midpoints 10 and 20 with frequencies 3 and 1, estimated mean=(30+20)/4=12.5.
A helpful tutoring exercise changes the given values and asks the student to explain the method without copying the original worked solution. Identify the first incorrect decision before correcting arithmetic.
Seven-day revision plan
Day 1: identify the definitions. Day 2: work through the first example. Day 3: change the numbers. Day 4: attempt a mixed problem. Day 5: explain and correct mistakes. Day 6: connect the skill to another chapter. Day 7: retest independently after a delay.
Frequently asked questions
How do I start? Name the known quantities and what must be found. How can I check? Substitute the result into the original relationship, compare the units and test whether the magnitude makes sense. What should a tutor diagnose? The first mistaken step, not only the final answer.
Official syllabus and small-group tutorial context
Consult the 2027 SEC G2 Mathematics K210 syllabus for exact assessment requirements. The unchanged eduKateSG Mathematics reference describes three-pupil tutorials near Sixth Avenue. Confirm current Secondary 3 G2 class fit, tutor, fees, venue and timetable directly.
Related Secondary 3 G2 Mathematics guides
See Reverse Percentages, Quadratic Graphs and Estimated Mean.