The percentage of the runners who have times less than 14.4 sec is 0.15%
The times of all 15-year old who run a certain race are approximately normally distributed with a given mean of 18 sec and a standard deviation of 1.2 sec.
We know that,
where,
X = raw score = 14.4
μ = mean = 18
σ = standard deviation = 1.2
Putting the values,
Finding the probability from the z score table, we get
P(z < -3) = 0.00135 = 0.135%
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Question: The times of all 15-year-olds who run a certain race are approximately normally distributed with a given mean of 026-1 = 18 seconds and a standard deviation of 026-2. = 1.2 sec. What percentage of the runners have times less than 14.4 seconds?
0.15%
0.15%
0.30%
0.60%
2.50%
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