IDNLearn.com: Where curiosity meets clarity and questions find their answers. Get accurate answers to your questions from our community of experts who are always ready to provide timely and relevant solutions.
Sagot :
a. This information is given to you.
b. We want to find
[tex]\mathrm{Pr}\{X > 8.9\}[/tex]
so we first transform [tex]X[/tex] to the standard normal random variable [tex]Z[/tex] with mean 0 and s.d. 1 using
[tex]X = \mu + \sigma Z[/tex]
where [tex]\mu,\sigma[/tex] are the mean/s.d. of [tex]X[/tex]. Now,
[tex]\mathrm{Pr}\left\{\dfrac{X - 10.5}2 > \dfrac{8.9 - 10.5}2\right\} = \mathrm{Pr}\{Z > -0.8\} \\\\~~~~~~~~= 1 - \mathrm{Pr}\{Z\le-0.8\} \\\\ ~~~~~~~~ = 1 - \Phi(-0.8) \approx \boxed{0.7881}[/tex]
where [tex]\Phi(z)[/tex] is the CDF for [tex]Z[/tex].
c. The 76th percentile is the value of [tex]X=x_{76}[/tex] such that
[tex]\mathrm{Pr}\{X \le x_{76}\} = 0.76[/tex]
Transform [tex]X[/tex] to [tex]Z[/tex] and apply the inverse CDF of [tex]Z[/tex].
[tex]\mathrm{Pr}\left\{Z \le \dfrac{x_{76} - 10.5}2\right\} = 0.76[/tex]
[tex]\dfrac{x_{76} - 10.5}2 = \Phi^{-1}(0.76)[/tex]
[tex]\dfrac{x_{76} - 10.5}2 \approx 0.7063[/tex]
[tex]x_{76} - 10.5 \approx 1.4126[/tex]
[tex]x_{76} \approx \boxed{11.9126}[/tex]
We appreciate every question and answer you provide. Keep engaging and finding the best solutions. This community is the perfect place to learn and grow together. Find reliable answers at IDNLearn.com. Thanks for stopping by, and come back for more trustworthy solutions.