AI generatedStatisticsCourse skill

Finding a combined mean when group sizes differ

Finding a combined mean when group sizes differ.

  • Mean = total of values ÷ number of values.
  • Mean × count recovers a total. Combine totals before dividing by a combined count.
  • Keep exact values until the final rounding step.

Example 1

Group A has 8 values with mean 5. Group B has 12 values with mean 10. Find the combined mean to 2 d..

A totalConvert each mean back to a total.
B totalGroup sizes may differ, so do not simply average the means.
Combined meanAdd the totals and divide by the combined number of values.

Example 2

Group A has 9 values with mean 6. Group B has 12 values with mean 10. Find the combined mean to 2 d..

A totalConvert each mean back to a total.
B totalGroup sizes may differ, so do not simply average the means.
Combined meanAdd the totals and divide by the combined number of values.
MeanRound only this final value.

Your turn

Question 1

Group A has 10 values with mean 7. Group B has 12 values with mean 10. Find the combined mean to 2 d..

Check answer
A totalConvert each mean back to a total.
B totalGroup sizes may differ, so do not simply average the means.
Combined meanAdd the totals and divide by the combined number of values.
MeanRound only this final value.
Question 2

Group A has 11 values with mean 8. Group B has 12 values with mean 10. Find the combined mean to 2 d..

Check answer
A totalConvert each mean back to a total.
B totalGroup sizes may differ, so do not simply average the means.
Combined meanAdd the totals and divide by the combined number of values.
MeanRound only this final value.
Question 3

Group A has 12 values with mean 9. Group B has 12 values with mean 10. Find the combined mean to 2 d..

Check answer
A totalConvert each mean back to a total.
B totalGroup sizes may differ, so do not simply average the means.
Combined meanAdd the totals and divide by the combined number of values.
Question 4

Group A has 13 values with mean 10. Group B has 12 values with mean 11. Find the combined mean to 2 d..

Check answer
A totalConvert each mean back to a total.
B totalGroup sizes may differ, so do not simply average the means.
Combined meanAdd the totals and divide by the combined number of values.
Question 5

Group A has 14 values with mean 11. Group B has 12 values with mean 11. Find the combined mean to 2 d..

Check answer
A totalConvert each mean back to a total.
B totalGroup sizes may differ, so do not simply average the means.
Combined meanAdd the totals and divide by the combined number of values.
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