Chapter 12-13 Study Guide:

When sampling from a normal population, it is not unusual at all to get 71.1% or more within 1 SD of the mean. This occurred in about 30/100 or 30% of the trials in the simulation. Thus, it is definitely possible that the population of times is approximately normally distributed even though we did not get exactly 68% within 1 SD of the mean in ... ................
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