The empirical rule states that 99.7% of data observed with a normal distribution falls within three standard deviations, 95% of the data falls within two standard deviations and 68% of it falls within one standard deviation.
Since we are asked to determine the interval in which Annabelle's times fall within the 68% of her finishing times in the race, and the mean of said times is 62 seconds, we must calculate
[tex]\mu\pm\sigma=62\pm0.5=(61.5,62.5)[/tex]So the interval (61.5,62.5) represents the middle 68% of her finishing times.
