In a reality show, two judges independently provided marks base do the performance of the participants. If the marks provided by the second judge are given by Y = 10.5 + 2x, where X is the marks provided by the first judge. If the variance of the marks provided by the second judge is 100, then the variance of the marks provided by the first judge is:
Explanation
To find the variance of the marks provided by the first judge (X), given the relationship Y=10.5+2X and Var(Y)=100:
Recall the variance transformation formula: For a linear transformation Y=aX+b, the variance of Y is Var(Y)=a2×Var(X).
Identify the constant a: In the equation Y=10.5+2X, the value of a is 2.
Substitute the known values into the formula: Given Var(Y)=100 and a=2, then
100=22×Var(X).
Solve for Var(X):
100=4×Var(X)⇒Var(X)=4100=25.
Therefore, the variance of the marks provided by the first judge is 25.