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Nov 2020 p52 q3
3191
Pia runs 2 km every day and her times in minutes are normally distributed with mean 10.1 and standard deviation 1.3.
On 75% of days, Pia takes longer than t minutes to run 2 km. Find the value of t.
Solution
We are given that 75% of the time, Pia takes longer than t minutes. This implies that 25% of the time, she takes less than t minutes. We need to find the z-score corresponding to the 25th percentile of a standard normal distribution.
The z-score for the 25th percentile is approximately
(-0.674).