/*! 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 6 You are given five points with t... [FREE SOLUTION] | 91Ó°ÊÓ

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You are given five points with these coordinates:$$ \begin{array}{c|rrrrrrr} x & -2 & -1 & 0 & 1 & 2 \\ \hline y & 1 & 1 & 3 & 5 & 5 \end{array} $$ a. Use the data entry method on your scientific or graphing calculator to enter the \(n=5\) observations. Find the sums of squares and cross-products, \(S_{x x} S_{x y},\) and \(S_{y y}\) b. Find the least-squares line for the data. c. Plot the five points and graph the line in part \(b\). Does the line appear to provide a good fit to the data points? d. Construct the ANOVA table for the linear regression.

Short Answer

Expert verified
Answer: The equation of the least-squares line for the given data points is $$y = 1.2x + 3$$.

Step by step solution

01

Calculate sums of x, y, x^2, xy, and y^2

To obtain the sums of squares and cross-products, we need the sums of \(x, y, x^2, xy,\) and \(y^2\). We will start by listing the given data points and calculating the required sums: $$ \begin{array}{c|rrrrrrr} x & -2 & -1 & 0 & 1 & 2 \\ \hline y & 1 & 1 & 3 & 5 & 5 \end{array} $$ Now, we will calculate the required sums: - \(\sum x = -2 - 1 + 0 + 1 + 2 = 0\) - \(\sum y = 1 + 1 + 3 + 5 + 5 = 15\) - \(\sum x^2 = (-2)^2 + (-1)^2 + 0^2 + 1^2 + 2^2 = 10\) - \(\sum xy = (-2)(1) + (-1)(1) + 0(3) + 1(5) + 2(5) = 12\) - \(\sum y^2 = 1^2 + 1^2 + 3^2 + 5^2 + 5^2 = 61\)
02

Obtain S_xx, S_xy, and S_yy

Now, we will calculate the sums of squares and cross-products using the formulas: - \(S_{xx} = \sum x^2 - \frac{(\sum x)^2}{n} = 10 - \frac{0^2}{5} = 10\) - \(S_{xy} = \sum xy - \frac{(\sum x)(\sum y)}{n} = 12 - \frac{0\cdot15}{5} = 12\) - \(S_{yy} = \sum y^2 - \frac{(\sum y)^2}{n} = 61 - \frac{15^2}{5} = 16\)
03

Calculate the slope and intercept of the least-squares line

Next, we will find the slope (m) and intercept (b) of the least-squares line using the formulas: - \(m = \frac{S_{xy}}{S_{xx}} = \frac{12}{10} = 1.2\) - \(b = \bar{y} - m\bar{x} = \frac{\sum y}{n} - m\frac{\sum x}{n} = \frac{15}{5} - 1.2\frac{0}{5} = 3\) Thus, the least-squares line is given by the equation: $$y = 1.2x + 3$$
04

Plot the points and graph the line. Check if the line appears to be a good fit for the data points.

Now, we can plot the given points and the least-squares line found above on a graph. After doing so, visually inspect whether the line appears to be a good fit for the data points. This can be subjective but typically, if the line goes through or reasonably close to most of the data points, it can be considered a good fit.
05

Construct the ANOVA table for the linear regression.

To construct the ANOVA table, we need the following values: - SSR (Sum of Squares Regression): \(SSR = m^2 \cdot S_{xx} = 1.2^2 \cdot 10 = 14.4\) - SSE (Sum of Squares Error): \(SSE = S_{yy} - m^2 \cdot S_{xx} = 16 - 14.4 = 1.6\) - MST (Mean Square Total): \(MST = \frac{S_{yy}}{n - 1} = \frac{16}{5 - 1} = 4\) - MSR (Mean Square Regression): \(MSR = \frac{SSR}{1} = 14.4\) - MSE (Mean Square Error): \(MSE = \frac{SSE}{n - 2} = \frac{1.6}{5 - 2} = 0.533\) We can now create the ANOVA table with these values: $$ \begin{array}{c|c|c|c|c} \text{Source} & \text{SS} & \text{df} & \text{MS} & \text{F} \\ \hline \text{Regression} & 14.4 & 1 & 14.4 & 27 \\ \text{Error} & 1.6 & 3 & 0.533 & - \\ \hline \text{Total} & 16 & 4 & 4 & - \end{array} $$ The ANOVA table is now complete.

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Key Concepts

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

ANOVA Table
The ANOVA (Analysis of Variance) Table is an essential tool in linear regression analysis, particularly when evaluating the fit of a regression model. This table provides a detailed breakdown of the variability observed in the data. It is structured into different components that help us understand how well our regression line fits the data points.
  • Source: This column in the ANOVA table lists the sources of variation, typically including Regression, Error, and Total.
  • SS (Sum of Squares): This column represents the sum of squares for each source of variation. It shows how much of the total variability of the outcomes (y-values) can be accounted for by the model (regression) and how much is left unexplained (error).
  • df (Degrees of Freedom): This column shows the degrees of freedom associated with each sum of squares. For regression, it is typically 1, while for error, it depends on the sample size and the number of predictors in the model.
  • MS (Mean Square): Mean Square is calculated by dividing the Sum of Squares by the related degrees of freedom. It helps to normalize the sum of squares, providing a more interpretable measure of variability.
  • F (F-Ratio): The F-ratio is computed by dividing the Mean Square of the Regression by the Mean Square of the Error. It is used to determine the significance of the regression model.
By analyzing the values in this table, such as the F-ratio, one can determine if the regression model significantly explains the variability in the data. A higher F-ratio typically indicates a more successful model fit.
Least-Squares Line
The Least-Squares Line is a fundamental concept in linear regression analysis. It represents the best-fit line through a set of data points, minimizing the sum of the squares of the vertical distances of the points from the line. The goal is to make these distances, known as residuals, as small as possible.
The equation of the least-squares line is given by:\[ y = mx + b \]
  • m (Slope): The slope indicates how much y changes for a one-unit change in x. It captures the strength and direction of the linear relationship.
  • b (Intercept): The intercept is the value of y when x is zero. It represents the point where the line crosses the y-axis.
To calculate the slope (m), use the formula:\[ m = \frac{S_{xy}}{S_{xx}} \]and for the intercept (b), the formula is:\[ b = \bar{y} - m\bar{x} \]These calculations help determine the line that best fits the data according to the least-squares criterion, making it a critical tool for predictions and understanding relationships between variables.
Sum of Squares
The Sum of Squares is a statistical measure that quantifies the variability in a dataset. It is a key component in calculating various metrics in regression analysis, such as explaining how well the model fits the data.
The main types of Sum of Squares are:
  • Total Sum of Squares (SST): It measures the total variance in the observed data and is given by the formula:\[ SST = \sum (y_i - \bar{y})^2 \]It represents the total variability to be explained by the model.
  • Sum of Squares Regression (SSR): This represents the portion of the variance explained by the model. It is computed with:\[ SSR = m^2 \cdot S_{xx} \]
  • Sum of Squares Error (SSE): It measures the variability that is not explained by the model, calculated as:\[ SSE = S_{yy} - SSR \]
These calculations form the basis of the ANOVA table and help in understanding the effectiveness of the regression model. By detailing how much of the variation is explained versus unexplained, these sums of squares give insight into the model's performance and potential areas for improvement.

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Most popular questions from this chapter

Refer to the data given in Exercise \(12.28 .\) The MINI TAB printout is reproduced here.Regression Analysis: y versus \(x\) The regregsion equation is \(y=-26.8+1.26 x\) \(\begin{array}{rrrr}\text { Coef } & \text { SB Coef } & \text { T } & \text { P } \\ -26.82 & 14.76 & -1.82 & 0.086 \\ 1.2617 & 0.1685 & 7.49 & 0.000\end{array}\) Predictor Constant X \(S=7.61912 \quad \mathrm{R}-\mathrm{Sq}=75.7 \mathrm{k} \quad \mathrm{R}-\mathrm{Sq}(\mathrm{ad} j)=74.3 \mathrm{k}\) Analyais of Variance a. What assumptions must be made about the distribution of the random error, \(\varepsilon\) ? b. What is the best estimate of \(\sigma^{2}\), the variance of the random error, \(\varepsilon\) ? c. Use the diagnostic plots for these data to comment on the validity of the regression assumptions.

An experiment was conducted to observe the effect of an increase in temperature on the potency of an antibiotic. Three 1 -ounce portions of the antibiotic were stored for equal lengths of time at each of these temperatures: \(30^{\circ}, 50^{\circ}, 70^{\circ},\) and \(90^{\circ} .\) The potency readings observed at each temperature of the experimental period are listed here: $$ \begin{array}{l|l|l|l|l} \text { Potency Readings, } y & 38,43,29 & 32,26,33 & 19,27,23 & 14,19,21 \\ \hline \text { Temperature, } x & 30^{\circ} & 50^{\circ} & 70^{\circ} & 90^{\circ} \end{array} $$ Use an appropriate computer program to answer these questions: a. Find the least-squares line appropriate for these data. b. Plot the points and graph the line as a check on your calculations. c. Construct the ANOVA table for linear regression. d. If they are available, examine the diagnostic plots to check the validity of the regression assumptions. e. Estimate the change in potency for a 1 -unit change in temperature. Use a \(95 \%\) confidence interval. f. Estimate the average potency corresponding to a temperature of \(50^{\circ} .\) Use a \(95 \%\) confidence interval. g. Suppose that a batch of the antibiotic was stored at \(50^{\circ}\) for the same length of time as the experimental period. Predict the potency of the batch at the end of the storage period. Use a \(95 \%\) prediction interval.

A social skills training program was implemented with seven mildly challenged students in a study to determine whether the program caused improvement in pre/post measures and behavior ratings. For one such test, the pre- and post test scores for the seven students are given in the table. $$ \begin{array}{lrr} \text { Subject } & \text { Pretest } & \text { Posttest } \\ \hline \text { Earl } & 101 & 113 \\ \text { Ned } & 89 & 89 \\ \text { Jasper } & 112 & 121 \\ \text { Charlie } & 105 & 99 \\ \text { Tom } & 90 & 104 \\ \text { Susie } & 91 & 94 \\ \text { Lori } & 89 & 99 \end{array} $$ a. What type of correlation, if any, do you expect to see between the pre- and posttest scores? Plot the data. Does the correlation appear to be positive or negative? b. Calculate the correlation coefficient, \(r\). Is there a significant positive correlation?

The Academic Performance Index (API) is a measure of school achievement based on the results of the Stanford 9 Achievement test. Scores range from 200 to 1000 , with 800 considered a long- range goal for schools. The following table shows the API for eight elementary schools in Riverside County, California, along with the percent of students at that school who are considered "English Learners" (EL). \(^{3}\) $$ \begin{array}{lcrrrrrrrr} \text { School } & 1 & 2 & 3 & 4 & 5 & 6 & 7 & 8 \\\ \hline \text { API } & 745 & 808 & 798 & 791 & 854 & 688 & 801 & 751 \\ \text { EL } & 71 & 18 & 24 & 50 & 17 & 71 & 11 & 57 \end{array} $$ a. Which of the two variables is the independent variable and which is the dependent variable? Explain your choice. b. Use a scatter plot to plot the data. Is the assumption of a linear relationship between \(x\) and \(y\) reasonable? c. Assuming that \(x\) and \(y\) are linearly related, calculate the least-squares regression line. d. Plot the line on the scatter plot in part b. Does the line fit through the data points?

Some varieties of nematodes, roundworms that live in the soil and feed on the roots of lawn grasses and other plants, can be treated by the application of nematicides. Data collected on the percent kill of nematodes for various rates of application (dosages given in pounds per acre of active ingredient) are as follows: $$ \begin{array}{l|l|l|l|l} \text { Rate of Application, } x & 2 & 3 & 4 & 5 \\\ \hline \text { Percent Kill, } y & \mid 50,56,48 & 63,69,71 & 86,82,76 & 94,99,97 \end{array} $$ Use an appropriate computer printout to answer these questions: a. Calculate the coefficient of correlation \(r\) between rates of application \(x\) and percent kill \(y .\) b. Calculate the coefficient of determination \(r^{2}\) and interpret. c. Fit a least-squares line to the data. per acre. What do the diagnostic plots tell you about the validity of the regression assumptions? Which assumptions may have been violated? Can you explain why? d. Suppose you wish to estimate the mean percent kill for an application of 4 pounds of the nematicide

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