/*! 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 102 The article "The Load-Life Relat... [FREE SOLUTION] | 91Ó°ÊÓ

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The article "The Load-Life Relationship for M50 Bearings with Silicon Nitride Ceramic Balls" (Lubricat. Engrg., 1984: 153-159) reports the accompanying data on bearing load life (million revs.) for bearings tested at a \(6.45-\mathrm{kN}\) load. \(\begin{array}{rrrrrrr}47.1 & 68.1 & 68.1 & 90.8 & 103.6 & 106.0 & 115.0 \\\ 126.0 & 146.6 & 229.0 & 240.0 & 240.0 & 278.0 & 278.0 \\ 289.0 & 289.0 & 367.0 & 385.9 & 392.0 & 505.0 & \end{array}\) a. Construct a normal probability plot. Is normality plausible? b. Construct a Weibull probability plot. Is the Weibull distribution family plausible?

Short Answer

Expert verified
Create both normal and Weibull probability plots and check for linear patterns.

Step by step solution

01

Organize the Data

First, arrange the dataset in ascending order. This makes it easier to interpret the ranks and percentiles needed for probability plotting.
02

Normal Probability Plot Preparation

To construct a normal probability plot, compute or use statistical software to determine the percentiles for a standard normal distribution, which will act as expected values under normality.
03

Create the Normal Probability Plot

Plot each data value against its corresponding normal percentile. This plot helps visualize if the points lie approximately on a straight line. If so, this suggests that the data follows a normal distribution.
04

Analyze the Normal Probability Plot

Inspect the plotted points. If most data points fall along the reference line, the normality assumption is reasonable. Look for systematic deviations from the line as indications of non-normality.
05

Weibull Probability Plot Preparation

For a Weibull probability plot, calculate the Weibull percentiles or use statistical software to generate the expected Weibull distribution values based on the rank of each data point.
06

Create the Weibull Probability Plot

Plot the logarithm of each data value against the Weibull percentiles. If the data aligns closely to a straight line, it suggests that the data follows a Weibull distribution.
07

Analyze the Weibull Probability Plot

Assess how closely the data follows a linear pattern on the plot. Deviations from a straight line suggest that the Weibull distribution might not be adequate.

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Key Concepts

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

Normal Distribution
The normal distribution, also known as the Gaussian distribution, is a continuous probability distribution characterized by its bell-shaped curve. It is widely used in statistics due to its properties. Its importance lies in the fact that many natural phenomena follow a normal distribution.

Some key properties include:
  • The curve is symmetric around the mean.
  • The mean, median, and mode of the distribution are equal.
  • About 68% of the data falls within one standard deviation of the mean.
  • Approximately 95% of the data falls within two standard deviations of the mean.
Understanding normal distribution is crucial in determining how data behaves under various circumstances. A normal probability plot is a graphical tool used to determine if a dataset approximates a normal distribution. If the points on this plot form a straight line, it suggests normality. This technique helps in assessing statistical assumptions and is often supported by statistical software for accuracy.
Weibull Distribution
The Weibull distribution is a flexible probability distribution commonly used to model life data, reliability, and survival analysis. It is particularly useful in engineering fields for analyzing life data such as the longevity of mechanical components.

Some features of the Weibull distribution include:
  • It can model various types of data behavior with different shape parameters.
  • A shape parameter greater than 1 indicates that the failure rate increases over time.
  • A shape parameter less than 1 suggests a decreasing failure rate.
  • When the shape parameter is equal to 1, the Weibull distribution reduces to an exponential distribution.
A Weibull probability plot is a tool to check if data follows a Weibull distribution. By plotting these data points against the expected Weibull percentiles, one can visually analyze their alignment to a straight line, indicating the Weibull fit quality. This plot is essential for reliability assessments and is often implemented using statistical software.
Data Visualization
Data visualization is the graphical representation of information and data. It is a valuable tool for understanding complex datasets, revealing trends, and finding insights that may not be apparent from raw data.

Some benefits of data visualization include:
  • Making data analysis more accessible and engaging for diverse audiences.
  • Helping identify patterns, outliers, and correlations easier.
  • Enhancing memory recall of information presented visually.
  • Facilitating faster decision-making by presenting clear data interpretations.
In probability plotting, data visualization plays a crucial role in assessing distribution assumptions and fit quality. Visual tools such as probability plots simplify the analysis, allowing users to make informed decisions at a glance. Leveraging statistical software for creating such visualizations ensures precision and efficiency.
Statistical Software
Statistical software is essential for conducting complex data analysis efficiently and accurately. These tools offer a wide range of functionalities that make them indispensable in both academic and professional settings.

Key features of statistical software include:
  • Data organization and manipulation capabilities.
  • Advanced analytical functionality, including probability plotting and distribution fitting.
  • User-friendly interfaces that facilitate easy data input and interpretation.
  • Visualizations that are customizable and interpretable.
For probability plotting, statistical software automates the plotting process, allowing users to focus on analysis rather than calculations. It enables the creation of normal and Weibull probability plots seamlessly, ensuring that students and professionals can engage with statistical analysis more effectively. By utilizing these tools, one can confirm distribution assumptions in a reliable manner.

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Most popular questions from this chapter

A system consists of five identical components connected in series as shown: As soon as one component fails, the entire system will fail. Suppose each component has a lifetime that is exponentially distributed with \(\lambda=.01\) and that components fail independently of one another. Define events \(A_{i}=\\{i\) th component lasts at least \(t\) hours \(\\}, i=1, \ldots, 5\), so that the \(A_{i}\) 's are independent events. Let \(X=\) the time at which the system fails-that is, the shortest (minimum) lifetime among the five components. a. The event \(\\{X \geq t\\}\) is equivalent to what event involving \(A_{1}, \ldots, A_{5}\) ? b. Using the independence of the five \(A_{i}\) 's, compute \(P(X \geq t)\). Then obtain \(F(t)=P(X \leq t)\) and the pdf of \(X\). What type of distribution does \(X\) have? c. Suppose there are \(n\) components, each having exponential lifetime with parameter \(\lambda\). What type of distribution does \(X\) have?

Let \(X=\) the time (in \(10^{-1}\) weeks) from shipment of a defective product until the customer retums the product. Suppose that the minimum return time is \(\gamma=3.5\) and that the excess \(X-3.5\) over the minimum has a Weibull distribution with parameters \(\alpha=2\) and \(\beta=1.5\) (see the article "Practical Applications of the Weibull Distribution," Indust. Qual. Control, 1964: 71-78). a. What is the cdf of \(X\) ? b. What are the expected return time and variance of return time? [Hint: First obtain \(E(X-3.5)\) and \(V(X-3.5)\).] c. Compute \(P(X>5)\). d. Compute \(P(5 \leq X \leq 8)\).

Relative to the winning time, the time \(X\) of another runner in a \(10 \mathrm{~km}\) race has pdf \(f_{X}(x)=\) \(2 / x^{3}, x>1\). The reciprocal \(Y=1 / X\) represents the ratio of the time for the winner divided by the time of the other runner. Find the pdf of \(Y\). Explain why \(Y\) also represents the speed of the other runner relative to the winner.

A theoretical justification based on a material failure mechanism underlies the assumption that ductile strength \(X\) of a material has a lognormal distribution. Suppose the parameters are \(\mu=5\) and \(\sigma=.1\). a. Compute \(E(X)\) and \(V(X)\). b. Compute \(P(X>125)\). c. Compute \(P(110 \leq X \leq 125)\). d. What is the value of median ductile strength? e. If ten different samples of an alloy steel of this type were subjected to a strength test, how many would you expect to have strength of at least 125 ? f. If the smallest \(5 \%\) of strength values were unacceptable, what would the minimum acceptable strength be?

Suppose the diameter at breast height (in.) of trees of a certain type is normally distributed with \(\mu=8.8\) and \(\sigma=2.8\), as suggested in the article "Simulating a Harvester-Forwarder Softwood Thinning" (Forest Products J., May 1997: \(36-41)\). a. What is the probability that the diameter of a randomly selected tree will be at least 10 in.? Will exceed 10 in.? b. What is the probability that the diameter of a randomly selected tree will exceed 20 in.? c. What is the probability that the diameter of a randomly selected tree will be between 5 and 10 in.? d. What value \(c\) is such that the interval \((8.8-c\), \(8.8+c)\) includes \(98 \%\) of all diameter values? e. If four trees are independently selected, what is the probability that at least one has a diameter exceeding 10 in.?

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