/*! 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 15 The temperature reading from a t... [FREE SOLUTION] | 91Ó°ÊÓ

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The temperature reading from a thermocouple placed in a constant-temperature medium is normally distributed with mean \(\mu\), the actual temperature of the medium, and standard deviation \(\sigma\). What would the value of \(\sigma\) have to be to ensure that \(95 \%\) of all readings are within \(1^{\circ}\) of \(\mu\) ?

Short Answer

Expert verified
The value of \(\sigma\) must be 0.5 to ensure 95% of readings are within 1° of \(\mu\).

Step by step solution

01

Understanding the Problem

We need to determine the standard deviation, \(\sigma\), required so that 95% of the thermocouple readings fall within 1° of the true mean temperature, \(\mu\). This implies the readings are within the interval \((\mu - 1, \mu + 1)\).
02

Using the Empirical Rule

According to the empirical rule for normal distributions, approximately 95% of data should fall within 2 standard deviations (\(2\sigma\)) of the mean. But in this case, we are given a specific distance (1°).
03

Calculating \(\sigma\) Using the Normal Distribution Property

For 95% confidence within 1 unit of the mean, we need to find \(\sigma\) such that the z-score for the 95% interval is 2 standard deviations from the mean. Given the normal distribution properties, this suggests the interval width of 2 (since it covers both sides of the mean) must equal \(2\sigma\).
04

Solving for \(\sigma\)

We can set the equation based on the width: \[ 2 = 2\sigma \] Thus, solving for \(\sigma\) we get: \[ \sigma = \frac{2}{2} = 1 \]
05

Conclusion on \(\sigma\)

To ensure that 95% of all readings are within 1° of \(\mu\), \(\sigma\) must be such that \(2\sigma = 2\). Therefore, \(\sigma\) must be equal to 0.5.

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Key Concepts

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

Temperature Measurement
Temperature measurement in the context of this exercise involves understanding how accurate and precise a thermocouple is when measuring a constant-temperature medium. A thermocouple is a type of temperature sensor used in various scientific and industrial applications.
These devices work by measuring the voltage created at the junction of two different metals, which correlates to temperature.In a constant-temperature medium, the thermocouple readings should all be close to the true temperature (denoted as \( \mu \)). But, because of inherent measurement variations, the readings are spread around \( \mu \).
This spread is characterized by the normal distribution. A normal distribution is a probability distribution that is symmetric around the mean, meaning most of the readings cluster around the mean temperature, with fewer readings at the extremes.Understanding temperature measurement within this context is crucial to ensure that the thermocouple provides reliable readings. The more accurate the thermocouple, the closer its readings will be to the true temperature \( \mu \), reducing unnecessary measurement errors.
Standard Deviation Calculation
The calculation of standard deviation, represented as \( \sigma \), is fundamental in statistics to measure how spread out numbers are in a data set. In this exercise, it plays a key role in determining how much temperatures measured by the thermocouple vary from the average temperature \( \mu \).
A lower standard deviation indicates that the data points (temperature readings) tend to be closer to the mean, while a higher standard deviation indicates more spread.Here, the task is to find the right \( \sigma \) so that 95% of the thermocouple readings are within 1° of the mean temperature. Using the formula \( 2 = 2\sigma \) set by the width of the required interval, the result is \( \sigma = 0.5 \).
This means the temperature readings will consistently fall within the desired range with an appropriately low deviation from \( \mu \). Thus, calculating and understanding standard deviation is vital not only for accurate measurements but also for predicting the reliability of a sensor's readings.
Empirical Rule
The empirical rule is a cornerstone concept in statistics when dealing with normal distributions. Often called the 68-95-99.7 rule, it states that in a normal distribution:
  • 68% of data falls within one standard deviation (\( \sigma \)) of the mean.
  • 95% lie within two standard deviations (\( 2\sigma \)) of the mean.
  • 99.7% are within three standard deviations (\( 3\sigma \)) of the mean.
For our exercise, the empirical rule is used to establish that for 95% of readings to be within a 1° range of the mean, the range must encompass two standard deviations.
Thus, the equation \( 2\sigma = 2 \) helps us determine the necessary \( \sigma \) for the readings.This rule is primarily useful for its simplicity in forecasting intervals and understanding variability in data. It directly connects the spread of readings (or other data points) with the standard deviation, allowing us to easily calculate how much data falls within these predetermined intervals. Thus, the empirical rule is essential for making swift, informed conclusions about normally distributed data.

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Most popular questions from this chapter

If bolt thread length is normally distributed, what is the probability that the thread length of a randomly selected bolt is a. Within \(1.5 \mathrm{SDs}\) of its mean value? b. Farther than \(2.5 \mathrm{SD}\) from its mean value? c. Between 1 and \(2 \mathrm{SDs}\) from its mean value?

Suppose a particular state allows individuals filing tax returns to itemize deductions only if the total of all itemized deductions is at least \(\$ 5000\). Let \(X\) (in 1000 s of dollars) be the total of itemized deductions on a randomly chosen form. Assume that \(X\) has the pdf $$ f(x, \alpha)=\left\\{\begin{array}{cc} k / x^{\alpha} & x \geq 5 \\ 0 & \text { otherwise } \end{array}\right. $$ a. Find the value of \(k\). What restriction on \(\alpha\) is necessary? b. What is the cdf of \(X\) ? c. What is the expected total deduction on a randomly chosen form? What restriction on \(\alpha\) is necessary for \(E(X)\) to be finite? d. Show that \(\ln (X / 5)\) has an exponential distribution with parameter \(\alpha-1\).

A 12 -in. bar that is clamped at both ends is to be subjected to an increasing amount of stress until it snaps. Let \(Y=\) the distance from the left end at which the break occurs. Suppose \(Y\) has pdf $$ f(y)=\left\\{\begin{array}{cl} \left(\frac{1}{24}\right) y\left(1-\frac{y}{12}\right) & 0 \leq y \leq 12 \\ 0 & \text { otherwise } \end{array}\right. $$ Compute the following: a. The cdf of \(Y\), and graph it. b. \(P(Y \leq 4), P(Y>6)\), and \(P(4 \leq Y \leq 6)\) c. \(E(Y), E\left(Y^{2}\right)\), and \(V(Y)\) d. The probability that the break point occurs more than 2 in. from the expected break point. e. The expected length of the shorter segment when the break occurs.

Let \(X\) denote the temperature at which a certain chemical reaction takes place. Suppose that \(X\) has pdf $$ f(x)=\left\\{\begin{array}{cl} \frac{1}{9}\left(4-x^{2}\right) & -1 \leq x \leq 2 \\ 0 & \text { otherwise } \end{array}\right. $$ a. Sketch the graph of \(f(x)\). b. Determine the cdf and sketch it. c. Is 0 the median temperature at which the reaction takes place? If not, is the median temperature smaller or larger than 0? d. Suppose this reaction is independently carried out once in each of ten different labs and that the pdf of reaction time in each lab is as given. Let \(Y=\) the number among the ten labs at which the temperature exceeds 1. What kind of distribution does \(Y\) have? (Give the names and values of any parameters.)

Let \(X\) denote the time to failure (in years) of a certain hydraulic component. Suppose the pdf of \(X\) is \(f(x)=32 /(x+4)^{3}\) for \(x>0\). a. Verify that \(f(x)\) is a legitimate pdf. b. Determine the cdf. c. Use the result of part (b) to calculate the probability that time to failure is between 2 and 5 years. d. What is the expected time to failure? e. If the component has a salvage value equal to \(100 /(4+x)\) when its time to failure is \(x\), what is the expected salvage value?

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