Answer :
The middle 99.7% is within 60 seconds to 63 seconds.
The empirical rule states that for a normal distribution, 68% are within one standard deviation from the mean, 95% are within two standard deviations from the mean and 99.7% are within three standard deviations from the mean.
Given that:
mean (μ) = 60 seconds, standard deviation (σ) = 1 second
99.7% are within three standard deviations = μ ± 3σ = 60 ± 3(1) = (57, 63)
The middle 99.7% is within 60 seconds to 63 seconds.
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