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The flow rate in a device used for air quality measurement depends on the pressure drop \(x\) (inches of water) across the device's filter. Suppose that for \(x\) values between 5 and 20 , these two variables are related according to the simple linear regression model with population regression line \(y=-0.12+0.095 x\). a. What is the mean flow rate for a pressure drop of 10 inches? A drop of 15 inches? b. What is the average change in flow rate associated with a 1 inch increase in pressure drop? Explain.

Short Answer

Expert verified
a. The mean flow rate for a pressure drop of 10 inches is \(0.83\) (flow rate units). The mean flow rate for a pressure drop of 15 inches is \(1.305\) (flow rate units). b. The average change in flow rate associated with a 1-inch increase in pressure drop is \(0.095\) (flow rate units).

Step by step solution

01

Determine the Mean Flow Rate for a Pressure Drop of 10 Inches

To find the average flow rate when the pressure drop is 10 inches, substitute \(x = 10\) into the equation of the regression line \(y = -0.12 + 0.095x\). The result of this calculation will give the flow rate response to a 10-inch pressure drop.
02

Determine the Mean Flow Rate for a Pressure Drop of 15 Inches

Repeat the previous process for a pressure drop of 15 inches. Substitute \(x = 15\) into the equation \(y = -0.12 + 0.095x\) and compute the result. This will give the response flow rate for a pressure drop of 15 inches.
03

Determine the Average Change in Flow Rate for an Increase of 1 Inch in Pressure Drop

The coefficient of \(x\) in the regression equation represents the average change in response (\(y\), the flow rate) for a unit change in the predictor (\(x\), the pressure drop). So, the coefficient of \(x\) in the equation \(y = -0.12 + 0.095x\), which is 0.095, represents the average change in flow rate for a 1-inch increase in pressure drop.

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Key Concepts

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

Mean Flow Rate
The mean flow rate is the average speed at which air moves through a device. This speed is crucial for understanding air quality as it impacts how efficiently air is filtered. In a linear regression model, the mean flow rate is predicted by substituting a given pressure drop value into the regression equation.
For instance, to find the mean flow rate with a pressure drop of 10 inches, you would plug 10 into the equation. Using the given linear regression equation, which is:
  • \( y = -0.12 + 0.095 \times x \)
Substituting 10 for \(x\), we calculate:
  • \( y = -0.12 + 0.095 \times 10 \)
  • \( y = -0.12 + 0.95 \)
  • \( y = 0.83 \)
Thus, the mean flow rate for a pressure drop of 10 inches is 0.83 units. Similarly, for 15 inches, you substitute 15:
  • \( y = -0.12 + 0.095 \times 15 \)
  • \( y = -0.12 + 1.425 \)
  • \( y = 1.305 \)
Therefore, the mean flow rate for a pressure drop of 15 inches is 1.305 units. This demonstrates how the mean flow rate increases as the pressure drop increases.
Pressure Drop
Pressure drop refers to the reduction in pressure as air passes through a filter in an air quality measurement device. It is essential in understanding how pressure variations can affect air flow rates. The pressure drop is the independent variable, represented by \(x\), in our regression model.
This means changes in the pressure drop directly affect the dependent variable, which is the mean flow rate. As pressure drop increases, more force is applied to the air passing through the filter, which typically increases flow rate.
By using regression models, we can predict how particular values of pressure drop affect flow rates, allowing for precise airflow control and improved air filtering efficiency. This understanding is crucial for ensuring devices maintain optimal performance and air quality.
Regression Equation
A regression equation is a mathematical model used to describe the relationship between two variables. It allows us to predict the value of one variable based on the other. In our case, we have a simple linear regression equation that models the relationship between pressure drop and flow rate. The equation is:
  • \( y = -0.12 + 0.095x \)
Here, \(y\) represents the flow rate and \(x\) is the pressure drop. The equation consists of two main parts:
  • The intercept: \(-0.12\), which represents the theoretical flow rate when the pressure drop is zero. However, in practical terms, it helps to underpin the model's foundation.
  • The slope: \(0.095\), showing the rate of change in flow rate for every inch of pressure drop. This coefficient is crucial as it indicates how sensitive the flow rate is to changes in pressure drop.
Regression equations like this are powerful tools in evaluating and predicting airflow efficiency in air quality devices.
Average Change
The average change in a regression context helps us understand how much the dependent variable (flow rate) shifts with every unit increase in the independent variable (pressure drop).
This concept is represented by the slope in our regression equation. The slope here is \(0.095\), indicating that for each 1 inch increase in pressure drop, the flow rate increases by 0.095 units.
This value is critical because it quantifies the responsiveness of the flow rate to changes in pressure drop. Such information allows engineers and technicians to gauge how modifications in pressure might alter air filtration efficiency.
Knowing the average change allows us to fine-tune air quality devices to deliver consistent and reliable performance, ensuring optimal air quality.

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Most popular questions from this chapter

Exercise 13.10 presented \(y=\) hardness of molded plastic and \(x=\) time elapsed since the molding was completed. Summary quantities included $$ n=15 \quad b=2.50 \quad \text { SSResid }=1235.470 $$ \(\sum(x-\vec{x})^{2}=4024.20\) a. Calculate the estimated standard deviation of the statistic \(b\) b. Obtain a \(95 \%\) confidence interval for \(\beta,\) the slope of the population regression line. c. Does the interval in Part (b) suggest that \(\beta\) has been precisely estimated? Explain.

A simple linear regression model was used to describe the relationship between \(y=\) hardness of molded plastic and \(x=\) amount of time elapsed since the end of the molding process. Summary quantities included \(n=\) \(15,\) SSResid \(=1235.470,\) and \(\mathrm{SSTo}=25,321.368 .\) a. Calculate a point estimate of \(\sigma .\) On how many degrees of freedom is the estimate based? b. What percentage of observed variation in hardness can be explained by the simple linear regression model relationship between hardness and elapsed time?

The shelf life of packaged food depends on many factors. Dry cereal is considered to be a moisturesensitive product (no one likes soggy cereal!) with the shelf life determined primarily by moisture content. In a study of the shelf life of one particular brand of cereal, \(x=\) time on shelf (days stored at \(73^{\circ} \mathrm{F}\) and \(50 \%\) relative humidity) and \(y=\) moisture content (\%) were recorded. The resulting data are from "Computer Simulation Speeds Shelf Life Assessments" (Package Engineering [1983]\(: 72-73)\). a. Summary quantities are $$ \sum x=269 \quad \sum y=51 \quad \sum x y=1081.5 $$ \(\sum y^{2}=190.78 \quad \sum x^{2}=7745\) Find the equation of the estimated regression line for predicting moisture content from time on the shelf. b. Does the simple linear regression model provide useful information for predicting moisture content from knowledge of shelf time? c. Find a \(95 \%\) interval for the moisture content of an individual box of cereal that has been on the shelf 30 days. d. According to the article, taste tests indicate that this brand of cereal is unacceptably soggy when the moisture content exceeds 4.1. Based on your interval in Part (c), do you think that a box of cereal that has been on the shelf 30 days will be acceptable? Explain.

The accompanying summary quantities for \(x=\) particulate pollution \(\left(\mu \mathrm{g} / \mathrm{m}^{3}\right)\) and \(y=\) luminance \((.01 \mathrm{~cd} /\) \(\mathrm{m}^{2}\) ) were calculated from a representative sample of data that appeared in the article "Luminance and Polarization of the Sky Light at Seville (Spain) Measured in White Light" (Atmospheric Environment [1988]\(: 595-599) .\) $$ \begin{aligned} n &=15 & \sum x=860 & \sum y=348 \\ \sum x^{2} &=56,700 & \sum y^{2}=8954 & \sum x y=22,265 \end{aligned} $$ a. Test to see whether there is a positive correlation between particulate pollution and luminance in the population from which the data were selected. b. What proportion of observed variation in luminance can be attributed to the approximate linear relationship between luminance and particulate pollution?

A sample of \(n=10,000(x, y)\) pairs resulted in \(r=.022 .\) Test \(H_{0}: \rho=0\) versus \(H_{a}: \rho \neq 0\) at significance level .05. Is the result statistically significant? Comment on the practical significance of your analysis.

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