The average waist size of the population is 85 cm, and the standard deviation is 15 cm. then A sample mean waist size of at least 86.3 cm has a 0.931 probability of occurring.
We can use the Z-score formula to find the probability.
Z = (86.3 - 85) / (15 / sqrt(277))
Z = 0.2 / 0.106
Z = 1.89
The probability of a sample mean waist size of at least 86.3 cm is 0.931.
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