Question

a) The average height of sunflowers in a field is 64 inches with a standard deviation of 3.5 inches. Describe a normal curve for the distribution, including the values on the horizontal axis at one, two, and three standard deviations from the mean. b) If there are 3,000 plants in the field, approximately how many will be taller than 71 inches?

Answer 1

The values on the horizontal axis are:
at 0 = 64
at one standard deviation (lower, upper) = (60.5 , 67.5)
at two standard deviation (lower, upper) = (57 , 71)
at three standard deviation (lower, upper) = (53.5 , 74,5)

B. P(x > 71) = 1 - P(x < 71) = 1 - P[z < (71 - 64)/3.5] = 1 - P(z < 2) = 1 - 0.97725 = 0.02275
Therefore the no of plants taller than 71 inches will be approximately 0.02275 * 3000 = 68