This is an independent topic guide, not the official syllabus. Compare it with the current paper outline and rules published by the examination authority.
01 / UNDERSTANDING
Learning objectives
Cover total-count relationships, combined averages and missing observations. Explain the weight of each group explicitly rather than treating every average as one equally important data point.
02 / UNDERSTANDING
The concept in context
An average equals a total divided by a count. To combine groups, reconstruct each total by multiplying its average by its size, add those totals and divide by the combined count. Averaging the group averages directly is valid only when the groups have equal sizes under the stated setup.
03 / UNDERSTANDING
A worked learning case
Original educational case. Ten trainees average 60 points and twenty trainees average 75 points on an original diagnostic. Their totals are 600 and 1,500, giving 2,100 points across thirty trainees. The combined average is 70, not 67.5. The larger group has the higher average, so the combined result lies closer to 75.
ORIGINAL EDUCATIONAL PRACTICE
Try it before you check.
Original practice: Five values average 20 and fifteen values average 40. What is their combined average?
Show the answer and reasoning
35.
The first group totals 5 × 20 = 100 and the second totals 15 × 40 = 600. Their combined total of 700 is spread across twenty values, giving 35. It lies between 20 and 40 and closer to 40, which is sensible because that group is three times larger.
Two traps to watch for.
- Taking the simple mean of unequal-group averages.
- Adding averages without reconstructing the underlying totals.
YOUR TOPIC-SPECIFIC LEARNING MAP
Your revision map
Convert each average back to a total.
Write the combined observation count.
Check the answer lies within the original range.
Explain the idea, apply it to a new situation, then check what changed in your reasoning.
BANKERS TUTORIAL · SOURCE NOTES
Keep the source alongside your notes.
Official links provide subject context and authoritative reference material. This guide’s explanation, scenario and question are original Bankers Tutorial learning content.
- sbi.bank.in https://sbi.bank.in/web/careers/current-openings
- sbi.bank.in https://sbi.bank.in/webfiles/uploads/files_2627/09/SBI_JA-Customer_Support_Sales-IH_Pre-2026-27_Eng.pdf
For SBI preparation, check the current official notice before relying on changing dates, rules or examination requirements.
