Avoiding an accident while driving can depend on reaction time. That time, measured from the moment the driver notices the danger until he applies the brake, is thought to follow a Normal model with a mean of 1.5 seconds and a standard deviation of 0.2 seconds.
What percent of drivers have a reaction time less than 1.3 seconds?

Can someone please just explain to me how to do this ? I'm not asking for an answer, I just need an explanation.

Question

Avoiding an accident while driving can depend on reaction time. That time, measured from the moment the driver notices the danger until he applies the brake, is thought to follow a Normal model with a mean of 1.5 seconds and a standard deviation of 0.2 seconds.
What percent of drivers have a reaction time less than 1.3 seconds?

Can someone please just explain to me how to do this ? I'm not asking for an answer, I just need an explanation.

jim_thompson5910 · Answer

you can use wolfram alpha as a calculator to calculate this probability I'm using the normal cdf function on that site and I got this http://www.wolframalpha.com/input/?i=normal+cdf&a=*MC.normal+cdf-_*Formula.dflt-&f2=1.3&x=0&y=0&f=NormalProbabilities.z_1.3&f3=1.5&f=NormalProbabilities.mu_1.5&f4=0.2&f=NormalProbabilities.sigma_0.2&a=*FVarOpt.1-_***NormalProbabilities.z--.***NormalProbabilities.pr--.**NormalProbabilities.l-.*NormalProbabilities.r---.**NormalProbabilities.mu-.*NormalProbabilities.sigma--- The answer you want is next to where you see "z < 1.3"