Answer:
a. 7% b. 1.4 inches
Step-by-step explanation:
(a)What is the probability that the diameter of a randomly selected tree will be at least 10 inches? Will exceed 10 inches.
Since our mean, x = 8.8 and standard deviation, σ = 2.8, and we want our maximum value to be 10 inches,
So, x + ε = 10 where ε = error between mean and maximum value
So,8.8 + ε = 10
ε = 10 - 8.8 = 1.2
Since σ = 2.8, ε/σ = 1.2/2.8 = 0.43
ε/σ × 100 % = 0.43 × 100 = 43%
Since 50% of our values are in the range x - 3σ to x and 43% of our values are in the range x to x + ε = x + 0.43σ, the probability of finding a value less than 10 inches is thus 50 % + 43% = 93%.
So, the probability of finding a value greater than 10 inches is thus 100 % - 93 % = 7 %.
(b) What is the value of c so that the interval (8.8-c, 8.8+c) contains 98% of all diameter values.
Since 98% of the values range from 8.8-c to 8.8+c, then half of the interval is from 8,8 - c to 8.8 or 8.8 to 8.8 + c. So, the number that range in this half interval is 98%/2 = 49%
So, c/σ × 100 % = 49%
c/σ = 0.49
c = 0.49σ = 0.49 × 2.8 = 1.372 ≅ 1.37 inches = 1.4 inches to 1 d.p
