- A76.8
- B8.76
- C7.2
- D7.27
Step-by-Step Solution
Combined mean . Variance , SD . (7.27 ignores the gap between the group means; 76.8 is the variance.)
Answer: B) 8.76
Group P has 40 values with mean 50 and SD 6; group Q has 60 values with mean 60 and SD 8. What is the standard deviation of all 100 values together?
Competition practiceStatistics
Master this topic in 30 minutes a day.
Don't just memorise the answer — build a daily practice habit.
Practice 5 Similar Questions Free →All Statistics practice questions
More Statistics practice
Twenty-five values have mean 40 and SD 5. It is later found that a value recorded as 52…A data set has a coefficient of variation of 25%. When 10 is added to every value, the…Eighteen observations have mean 7 and standard deviation 4. The observation 12 is then…Ten observations have variance 9. Each is multiplied by 2 and then 3 is added; after…For n observations, Σ(x − 5) = 20 and Σ(x − 5)² = 160, and their mean is 6. Find n and…