/*! 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 11 Suppose that in a certain chemic... [FREE SOLUTION] | 91Ó°ÊÓ

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Suppose that in a certain chemical process the reaction time \(y\) (hr) is related to the temperature \(\left({ }^{\circ} \mathrm{F}\right)\) in the chamber in which the reaction takes place according to the simple linear regression model with equation \(y=5.00-.01 x\) and \(\sigma=.075\). a. What is the expected change in reaction time for a \(1^{\circ} \mathrm{F}\) increase in temperature? For a \(10^{\circ} \mathrm{F}\) increase in temperature? b. What is the expected reaction time when temperature is \(200^{\circ} \mathrm{F}\) ? When temperature is \(250^{\circ} \mathrm{F}\) ? c. Suppose five observations are made independently on reaction time, each one for a temperature of \(250^{\circ} \mathrm{F}\). What is the probability that all five times are between \(2.4\) and \(2.6 \mathrm{~h}\) ? d. What is the probability that two independently observed reaction times for temperatures \(1^{\circ}\) apart are such that the time at the higher temperature exceeds the time at the lower temperature?

Short Answer

Expert verified
For each 1°F increase, time decreases by 0.01 hr. Reaction time is 3.00 hr at 200°F, 2.50 hr at 250°F, and probability of all times 2.4-2.6 hr is 0.336. Probability for higher temp exceeding is 0.538.

Step by step solution

01

Determine change for 1° F

The regression model equation is given by \( y = 5.00 - 0.01x \). The coefficient of \( x \) (which is \(-0.01\)) represents the change in \( y \) (reaction time) for a 1° F change in temperature. Therefore, for a \( 1^{\circ} \mathrm{F} \) increase in temperature, the expected change in reaction time is \(-0.01\) hours.
02

Determine change for 10° F

To find the change in reaction time for a \( 10^{\circ} \mathrm{F} \) increase, multiply the change per degree by 10. Therefore, \(-0.01 \times 10 = -0.10\) hours is the change in reaction time for a \( 10^{\circ} \mathrm{F} \) increase.
03

Calculate expected reaction time at 200°F

Substitute \( x = 200 \) into the regression model equation \( y = 5.00 - 0.01x \):\[ y = 5.00 - 0.01 \times 200 = 3.00 \] The expected reaction time when the temperature is \( 200^{\circ} \mathrm{F} \) is 3.00 hours.
04

Calculate expected reaction time at 250°F

Substitute \( x = 250 \) into the model equation \( y = 5.00 - 0.01x \):\[ y = 5.00 - 0.01 \times 250 = 2.50 \] The expected reaction time when the temperature is \( 250^{\circ} \mathrm{F} \) is 2.50 hours.
05

Calculate probability for times between 2.4 and 2.6 h

For a temperature of \( 250^{\circ} \mathrm{F} \), the expected reaction time is 2.50 hours with \( \sigma = 0.075 \). The standard deviation for five observations is \( \frac{\sigma}{\sqrt{5}} = \frac{0.075}{\sqrt{5}} \approx 0.0335 \). Evaluate \( P(2.4 < y < 2.6) \) using the standard normal table:1. Calculate the z-scores: \( z_1 = \frac{2.4 - 2.5}{0.075} = -1.33 \) and \( z_2 = \frac{2.6 - 2.5}{0.075} = 1.33 \)2. Using the standard normal distribution table, find \( P(-1.33) \approx 0.0918 \) and \( P(1.33) \approx 0.9082 \).3. Thus, \( P(2.4 < y < 2.6) = 0.9082 - 0.0918 = 0.8164 \).Therefore, the probability that all five times are between 2.4 and 2.6 hours is approximately \( (0.8164)^5 \approx 0.336 \).
06

Probability that time at higher temperature exceeds lower

For temperatures \( x \) and \( x+1 \), the reaction times are \( y_x = 5.00 - 0.01x \) and \( y_{x+1} = 5.00 - 0.01(x + 1) \). The difference in reaction times is constant at \( 0.01 \). As \( \sigma = 0.075 \) is constant, we calculate \( P(y_{x+1} > y_x) = P(\epsilon_{x+1} - \epsilon_x > -0.01) \):1. Calculate the z-score \( z = \frac{-0.01}{\sqrt{0.075^2 + 0.075^2}} = \frac{-0.01}{0.106} \approx -0.094 \).2. Look up this z-score in the standard normal distribution table, \( P(Z > -0.094) \approx 0.5379 \).Therefore, the probability that time at the higher temperature exceeds time at the lower temperature is approximately \( 0.5379 \).

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Key Concepts

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

Reaction Time
Reaction time is the duration it takes for a chemical reaction to occur. In the context of our exercise, reaction time is denoted by the variable \( y \), measured in hours. The problem at hand uses a simple linear regression model to predict the reaction time based on the temperature \( x \) in degrees Fahrenheit. A linear regression model is essentially a mathematical equation that describes the relationship between two variables by fitting a line to data points. In our case, the model is represented by the equation \( y = 5.00 - 0.01x \). This means that for every 1 degree Fahrenheit increase in temperature, the reaction time decreases by 0.01 hours. Unfortunately, this isn't something you can simply observe. Thus, mathematic tools are employed to predict how each degree Fahrenheit affect the reaction speed.
It's crucial to know how to interpret this equation. The constant \( 5.00 \) is the intercept, which represents the predicted reaction time when the temperature is 0°F (although this might not be practical in real-world scenarios). The coefficient \( -0.01 \) indicates the rate of change of \( y \) (reaction time) with respect to \( x \) (temperature), highlighting the sensitivity of reaction time to temperature changes. Small variations in temperature can lead to noticeable differences in the reaction time.
Temperature Effect
Temperature holds a significant influence in chemical reactions. It can either speed up or slow down the process. In this exercise, the model tells us that increasing the temperature by 1°F decreases the reaction time by 0.01 hours. This concept is demonstrated by the negative coefficient in the regression equation \( y = 5.00 - 0.01x \). This indicates an inverse relationship between temperature and reaction time, meaning as one goes up, the other goes down.
At a temperature of 200°F, the expected reaction time is calculated by plugging the value into the equation \( y = 5.00 - 0.01 \times 200 \), producing a reaction time of 3.00 hours. Similarly, at 250°F, the expected reaction time is 2.50 hours. This showcases how much influence temperature possesses in altering reaction durations. The simplicity of these calculations further emphasizes the linear nature of the regression model.
Probability Calculation
Probability calculation is a statistical measure that can help us understand the likelihood or chance of an event occurring. In the exercise, we're tasked with finding the probability that five independently measured reaction times at a temperature of 250°F will fall between 2.4 and 2.6 hours.
To achieve this, we calculate the z-scores, which transform our data into a standard form that makes it easier to use the standard normal distribution table. For example, with an expected reaction time of 2.50 hours and standard deviation of 0.075, the z-score calculations for 2.4 and 2.6 hours provide us with the probability of each observation being within that range. According to our calculations, the probability that all five observations are between 2.4 and 2.6 hours is approximately 0.336. This involves using the knowledge that the standard deviation for a sample size of five is adjusted by dividing by the square root of the sample size, demonstrating a practical application of the central limit theorem.
Expected Value
Expected value is a core concept in probability and statistics, representing the mean or average outcome of a random variable. It portrays what you would "expect"
if you were to repeat an experiment many times. Here, the expected reaction time for given temperatures can be calculated directly using the regression equation.Using the linear model \( y = 5.00 - 0.01x \), you can determine the expected reaction time across temperature changes. For instance, at 200°F the expected reaction time is 3.00 hours, whereas at 250°F it is 2.50 hours.
Expected values help in making informed predictions about future outcomes. Understanding expected value in a regression context allows us to comprehend average responses effectively. This predictive power is crucial in numerous fields from finance to engineering, as it guides decision-making based on established patterns instead of random guesswork. It's a helpful tool for taking uncertainty into account and predicting outcomes that align with observed data.

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