/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 14 Use the data in the table below ... [FREE SOLUTION] | 91Ó°ÊÓ

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Use the data in the table below for sitting adult males and females (based on anthropometric survey data from Gordon, Churchill, et al.). These data are used often in the design of different seats, including aircraft seats, train seats, theater seats, and classroom seats. (Hint: Draw a graph in each case.) $$\begin{array}{|l|l|l|l|} \hline & \text { Mean } & \text { St. Dev. } & \text { Distribution } \\ \hline \text { Males } & 23.5 \mathrm{in} . & 1.1 \mathrm{in} . & \text { Normal } \\ \hline \text { Females } & 22.7 \mathrm{in} . & 1.0 \mathrm{in} . & \text { Normal } \\ \hline \end{array}$$ Find the probability that a female has a back-to-knee length greater than 24.0 in.

Short Answer

Expert verified
P(X > 24.0) = 0.0968

Step by step solution

01

- Understand the Problem

To find the probability that a female has a back-to-knee length greater than 24.0 inches, we need to use the normal distribution of the given data and perform a standard normal transformation.
02

- Identify Given Values

From the table, we know that the mean back-to-knee length for females is 22.7 inches, and the standard deviation is 1.0 inches. The length we are interested in is 24.0 inches.
03

- Standard Normal Transformation

We need to convert 24.0 inches to a z-score using the formula: $$z = \frac{x - \text{mean}}{\text{standard deviation}}$$ Substitute the values: $$z = \frac{24.0 - 22.7}{1.0} = 1.3$$
04

- Use Z-Table to Find Probability

Use the z-table to find the probability corresponding to a z-score of 1.3. The z-table gives the area to the left of the z-score. For a z-score of 1.3, the table value is 0.9032.
05

- Calculate the Desired Probability

We want the probability that the length is greater than 24.0 inches, which is the area to the right of the z-score. Subtract the z-table value from 1: $$P(X > 24.0) = 1 - P(Z < 1.3)$$ $$P(X > 24.0) = 1 - 0.9032 = 0.0968$$

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

z-score calculation
To understand the normal distribution probability, we must delve into z-score calculation first. The z-score, also known as the standard score, measures how many standard deviations an element is from the mean. This process helps us understand where a specific observation lies within a normal distribution.

The formula for calculating a z-score is simple: \(z = \frac{x - \text{mean}}{\text{standard deviation}}\).
Here, \(x\) is the value you want to convert, the \(\text{mean}\) is the average of the dataset, and \(\text{standard deviation}\) measures the dispersion of the dataset.
For instance, if the mean height of females is 22.7 inches with a standard deviation of 1.0 inch, and you want to find the z-score for a height of 24.0 inches, you substitute these values into the formula: \(z = \frac{24.0 - 22.7}{1.0} = 1.3\).
This means the height of 24.0 inches is \(1.3\) standard deviations above the mean.
standard normal transformation
Standard normal transformation is a vital concept when dealing with normal distribution probabilities. It usually involves converting a normal distribution to a standard normal distribution where the mean is zero and the standard deviation is one. This process is often termed 'standardizing'.

By transforming the data to the standard normal distribution, we make use of the z-table (or standard normal table) efficiently. As demonstrated in the original exercise, we transform an observed value \(24.0\) to a z-score \(1.3\). The transformed value is easier to work with for finding exact probabilities and comparing different datasets.

The formula to achieve this conversion is again: \(z = \frac{x - \text{mean}}{\text{standard deviation}}\).
This transformation aligns the data on a common scale, allowing seamless extrapolation of probabilities from the z-table. Remember, this transformation simplifies the pursuit of probability metrics across varied distributions.
probability finding using z-table
Once we calculate the z-score, the next step is to find the corresponding probability using the z-table. A z-table helps us work with the standard normal distribution and find the area (probability) to the left of any given z-score.

For example, from our previous calculation, the z-score of 1.3 corresponds to a probability of \(0.9032\). This value represents the probability that a randomly selected female will have a back-to-knee length less than 24.0 inches.
To find the probability of a value being greater than a specific z-score, we subtract this value from 1:

\(P(X > 24.0) = 1 - P(Z < 1.3)\)
\(P(X > 24.0) = 1 - 0.9032 = 0.0968\).
Therefore, there's about a \(9.68\)% chance that a randomly selected female will have a back-to-knee length greater than 24.0 inches. Working with the z-table empowers us to derive meaningful probabilities with straightforward arithmetic, making data insights more accessible.

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Most popular questions from this chapter

Find the indicated area under the curve of the standard normal distribution; then convert it to a percentage and fill in the blank. The results form the basis for the range rule of thumb and the empirical rule introduced in Section 3-2. About _____ \(\%\) of the area is between \(z=-1\) and \(z=1\) (or within 1 standard deviation of the mean).

Doorway Height The Boeing \(757-200\) ER airliner carries 200 passengers and has doors with a height of 72 in. Heights of men are normally distributed with a mean of 68.6 in. and a standard deviation of 2.8 in. (based on Data Set 1 "Body Data" in Appendix B). a. If a male passenger is randomly selected, find the probability that he can fit through the doorway without bending. b. If half of the 200 passengers are men, find the probability that the mean height of the 100 men is less than 72 in. c. When considering the comfort and safety of passengers, which result is more relevant: the probability from part (a) or the probability from part (b)? Why? d. When considering the comfort and safety of passengers, why are women ignored in this case?

A common design requirement is that an environment must fit the range of people who fall between the Sth percentile for women and the 95 th percentile for men. In designing an assembly work table, we must consider sitting knee height, which is the distance from the bottom of the feet to the top of the knee. Males have sitting knee heights that are normally distributed with a mean of 21.4 in. and a standard deviation of 1.2 in.; females have sitting knee heights that are normally distributed with a mean of 19.6 in. and a standard deviation of 1.1 in. (based on data from the Department of Transportation). a. What is the minimum table clearance required to satisfy the requirement of fitting \(95 \%\) of men? Why is the 95 th percentile for women ignored in this case? b. The author is writing this exercise at a table with a clearance of 23.5 in. above the floor. What percentage of men fit this table, and what percentage of women fit this table? Does the table appear to be made to fit almost everyone?

Unbiased Estimators Data Set 4 "Births" in Appendix B includes birth weights of 400 babies. If we compute the values of sample statistics from that sample, which of the following statistics are unbiased estimators of the corresponding population parameters: sample mean; sample median; sample range; sample variance; sample standard deviation; sample proportion?

Mensa Membership in Mensa requires a score in the top \(2 \%\) on a standard intelligence test. The Wechsler IQ test is designed for a mean of 100 and a standard deviation of \(15,\) and scores are normally distributed. a. Find the minimum Wechsler IQ test score that satisfies the Mensa requirement. b. If 4 randomly selected adults take the Wechsler IQ test, find the probability that their mean score is at least \(131 .\) c. If 4 subjects take the Wechsler test and they have a mean of 132 but the individual scores are lost, can we conclude that all 4 of them are eligible for Mensa?

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