The time that a skier takes on a downhill course has a normal distribution with a mean of 12.3 minutes and a standard deviation of 0.45 minutes.

Question

What is the probability that on a random run this skier takes less than 11 minutes?

Answer 1

Normalcdf(-10⁹,11,12.3,0.45) command in DISTR menu of TI-83+ calculator gives this probability 0.001933.

The 4 parameters correspond to a,b,μ,σ -- i.e. area under standard normal curve for scores equivalent to -infinity thru 11. 

 

Note: 11 minutes is 2.89 standard deviations to the left of the mean.