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The percentage of runners having times less than 14.4 sec is 0.15%. Then the correct option is A.
What is normal a distribution?
It is also called the Gaussian Distribution. It is the most important continuous probability distribution. The curve looks like a bell, so it is also called a bell curve.
The times of all 15-year-olds who run a certain race are approximately normally distributed with a given mean (μ) = 18 sec and standard deviation (σ) = 1.2 sec.
The runners have times less than 14.4 sec.
The z-score is a numerical measurement used in statistics of the value's relationship to the mean of a group of values, measured in terms of standards from the mean.
[tex]\rm z-score = \dfrac{X - \mu}{\sigma }\\\\z-score = \dfrac{14.4- 18}{1.2}\\\\z-score = -3[/tex]
Then the Percentage will be
[tex]\rm P(X < 14.4) = P(z < -3) = 0.0013499 = 0.13499\ \% \approx 0.15\ \%[/tex]
More about the normal distribution link is given below.
https://brainly.com/question/12421652
