Final answer:
To find the proportion of usable onions for each supplier, calculate the area under the normal distribution curve between the specified diameter range. Company B provides a higher proportion of usable onions compared to Company A.
Step-by-step explanation:
To find the proportion of usable onions for each supplier, we need to calculate the area under the normal distribution curve between the specified diameter range. For Company A, the mean diameter is 10.3 cm with a standard deviation of 1.2 cm. For Company B, the mean diameter is 10.6 cm with a standard deviation of 0.9 cm.
First, we calculate the z-scores for the lower and upper limits of the diameter range for each supplier. For Company A, the z-score for the lower limit (9 cm) is (9 - 10.3) / 1.2 = -1.08, and for the upper limit (10 cm) is (10 - 10.3) / 1.2 = -0.25. For Company B, the z-score for the lower limit is (9 - 10.6) / 0.9 = -1.78, and for the upper limit is (10 - 10.6) / 0.9 = -0.67.
Next, we use a standard normal distribution table (or a calculator) to find the proportion of the area under the curve between these z-scores. The proportion for Company A is P(-1.08 ≤ Z ≤ -0.25) = 0.3093 - 0.3997 = 0.0906, and for Company B is P(-1.78 ≤ Z ≤ -0.67) = 0.0375 - 0.2525 = 0.2150.
Therefore, Company B provides a higher proportion of usable onions compared to Company A.