Mean And Variance Of Random Variables

Step 1: Concept
The combined mean of two groups with sizes and means is given by .
Step 2: Analysis
Subtracting from the combined mean: . Since , this value is positive, so .
Step 3: Analysis
Subtracting from the combined mean: . Since , this value is negative, so .
Step 4: Conclusion
Therefore, the combined mean always lies between the two individual means: .
Final Answer: (d)