About 99.7% of vehicles whose speeds are between 59 miles per hour and 77 miles per hour.
Empirical rule states that for a normal distribution, 68% lie within one standard deviations, 95% lie within two standard deviations, and 99.7% lie within three standard deviations of the mean.
Given that mean (μ) = 68 miles per hour, standard deviation (σ) = 3 miles per hour.
68% lie within one standard deviation = (μ ± σ) = (68 ± 3) = (65, 71).
Hence 68% of the vehicle speed is between 65 miles per hour and 71 miles per hour.
95% lie within two standard deviation = (μ ± 2σ) = (68 ± 2*3) = (62, 74).
Hence 95% of the vehicle speed is between 62 miles per hour and 74 miles per hour.
99.7% lie within three standard deviation = (μ ± 3σ) = (68 ± 3*3) = (59, 77).
Hence 99.7% of the vehicle speed is between 59 miles per hour and 77 miles per hour.
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