a)
To draw a normal curve for the distribution of sunflower heights, we start by placing the average height of 64 in. at the center of the curve. Then, we mark one standard deviation above and below the mean, which would be 64 + 3.5 = 67.5 in. and 64 - 3.5 = 60.5 in. respectively. Next, we mark two standard deviations above and below the mean, which would be 71 in. and 57 in. Finally, we mark three standard deviations above and below the mean, which would be 74.5 in. and 53.5 in.
b)
To determine how many plants will be taller than 71 in., we calculate the z-score for a height of 71 in. using the formula z = (x - μ) / σ, where x is the height, μ is the mean (64 in.), and σ is the standard deviation (3.5 in.).
z = (71 - 64) / 3.5 = 2
Next, we look up the z-score of 2 in a standard normal distribution table to find out the proportion of plants taller than 71 in. We find that the proportion is approximately 0.0228 or 2.28%.
Finally, to find the number of plants taller than 71 in., we multiply the proportion by the total number of plants in the field:
Number of plants = 0.0228 * 3000 = 68.4
So, approximately 68 plants will be taller than 71 in.