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B) 1
First, find the mean of the quiz grades:
(97+95+97+94+93+99+91+96+94+88+92+91) / 12 = 94.5
Next, find the standard deviation:
1. Calculate the variance:
(97-94.5)² + (95-94.5)² + (97-94.5)² + (94-94.5)² + (93-94.5)² + (99-94.5)² + (91-94.5)² + (96-94.5)² + (94-94.5)² + (88-94.5)² + (92-94.5)² + (91-94.5)² / 12 = 8.75
2. Take the square root of the variance to find the standard deviation:
√8.75 ≈ 2.96
Since all the quiz grades fall within 1 standard deviation of the mean (94.5 +/- 2.96), the answer is B) 1.