Pure Mathematics
Statistics

Worked Example 6

The random variable [latex]X[/latex] is normally distributed with mean [latex]135[/latex] variance [latex]{{\sigma }^{2}}[/latex].

(i)

Given that [latex]\text{P}\left( 127a \right)=0.3865[/latex], show that [latex]\sigma =10.68[/latex], correct to the [latex]2[/latex] decimal places, and find the value of the constant [latex]a[/latex].

[latex]X[/latex] is related to a normal random variable [latex]Y[/latex] by formula [latex]X={{Y}_{1}}+{{Y}_{2}}-4[/latex], where [latex]{{Y}_{1}}[/latex] and [latex]{{Y}_{2}}[/latex] are two independent observations of [latex]Y[/latex].

(ii)

Find [latex]\text{E}\left( Y \right)[/latex] and [latex]\text{Var}\left( Y \right)[/latex].

Leave a Comment