Question

ree heights: Cherry trees in a certain orchard have heights that are normally distributed with mean μ = 119 inches and standard deviation σ = 17 inches. Use the TI-84 PLUS calculator to answer the following. Round the answers to at least four decimal places. (a) What proportion of trees are more than 130 inches tall? (b) What proportion of trees are less than 90 inches tall? (c) What is the probability that a randomly chosen tree is between 95 and 105 inches tall? Part: 0 / 30 of 3 Parts Complete Part 1 of 3 What proportion of trees are more than 130 inches tall? The proportion of trees that are more than 130 inches tall is .

Answer 1

a) 0.2588

b) 0.044015

c) 0.12609

Explanation:

Using the TI-84 PLUS calculator

The formula for calculating a z-score is is z = (x-μ)/σ,

where x is the raw score

μ is the population mean

σ is the population standard deviation.

From the question, we know that:

μ = 119 inches

standard deviation σ = 17 inches

(a) What proportion of trees are more than 130 inches tall?

x = 130 inches

z = (130-119)/17

= 0.64706

Probabilty value from Z-Table:

P(x<130) = 0.7412

P(x>130) = 1 - P(x<130) = 0.2588

(b) What proportion of trees are less than 90 inches tall?

x = 90 inches

z = (90-119)/17

=-1.70588

Probability value from Z-Table:

P(x<90) = 0.044015

(c) What is the probability that a randomly chosen tree is between 95 and 105 inches tall?

For x = 95

z = (95-119)/17

= -1.41176

Probability value from Z-Table:

P(x = 95) = 0.07901

For x = 105

z = (105 -119)/17

=-0.82353

Probability value from Z-Table:

P(x<105) = 0.2051

The probability that a randomly chosen tree is between 95 and 105 inches tall

P(x = 105) - P(x = 95)

0.2051 - 0.07901

= 0.12609