0 votes 0 votes If the marks obtained by the students in a competitive exam follows normal distribution with mean value 50 and variance 10. If the passing marks is 40 then percentage of failed students is ____% Manan Shah asked Dec 20, 2018 Manan Shah 346 views answer comment Share Follow See all 6 Comments See all 6 6 Comments reply Satbir commented Dec 20, 2018 i edited by Satbir Dec 20, 2018 reply Follow Share 2.4% i think S.D. should be 10 instead of variance.correct me if i am wrong. we have to calculate p(X<40) for normal distribution. =>p(z< (x − μ) / σ ) =p(z<-1) where x=40, μ =50 and σ = 10. p(z<-1) = (e^(-z^2 / 2)) / (σ√(2π)) =e^(-1/2)/(10*2.505) =e^-0.5/25.05 =0.606/25.05 =0.024 ans= 0.024*100%=2.4% 0 votes 0 votes Manan Shah commented Dec 20, 2018 reply Follow Share I don't have ans key but pls provide the solution @Satbir 0 votes 0 votes Satbir commented Dec 20, 2018 reply Follow Share now check 0 votes 0 votes Manan Shah commented Dec 20, 2018 reply Follow Share Seems like right I think @Satbir 0 votes 0 votes Mk Utkarsh commented Dec 20, 2018 reply Follow Share Manan Shah please recheck if variance is 10 or standard deviation 0 votes 0 votes Manan Shah commented Dec 20, 2018 reply Follow Share Already checked variance=10 given. It may be error @Mk Utkarsh 0 votes 0 votes Please log in or register to add a comment.