Consider the following statements: 1) Mean is independent of change in scale and change in origin. 2) Variance is independent of change in scale but not in origin. Which of the above statements is/are correct?
Consider the following statements: 1) Mean is independent of change in scale and change in origin. 2) Variance is independent of change in scale but not in origin. Which of the above statements is/are correct? Correct Answer Neither 1 nor 2
Concept:
Properties of mean:
- If C is added to each observation, then the new mean is also increased by C.
- If C is multiplied to each observation, then the new mean is also C times.
- If C is divided to each observation, then the new mean is also old mean divided by C.
Properties of variance:
- Var(X + C) = Var(X), where C is a constant.
- Var(CX) = C2 × Var(X), where C is a constant.
Calculation:
Mean:
Change in scale:
We know that, if C is multiplied to each observation, then new mean is also C times old mean.
So, mean is dependent on change in scale.
Change in origin:
We know that, if C is added/subtracted to each observation, then new mean is also increased/decreased by C.
So, mean is dependent on change in origin.
Variance:
Change in scale:
We know that, Var(CX) = C2 × Var(X), where C is a constant.
So, variance is dependent on change in scale.
Change in origin:
We know that, Var(X + C) = Var(X), where C is a constant.
So, variance is independent of change in origin.
Hence, both statement (1) & (2) are incorrect.