Chapter 12: Problem 4
Give the equation and graph for a line with \(y\) -intercept equal to -3 and slope equal to 1
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Chapter 12: Problem 4
Give the equation and graph for a line with \(y\) -intercept equal to -3 and slope equal to 1
These are the key concepts you need to understand to accurately answer the question.
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The table gives the numbers of Octolasmis tridens and \(O\). lowei barnacles on each of 10 lobsters. \({ }^{8}\) Does it appear that the barnacles compete for space on the surface of a lobster? $$ \begin{array}{ccc} \text { Lobster } & & \\ \text { Field Number } & \text { 0. tridens } & \text { 0. lowei } \\ \hline \text { A061 } & 645 & 6 \\\ \text { A062 } & 320 & 23 \\ \text { A066 } & 401 & 40 \\ \text { A070 } & 364 & 9 \\ \text { A067 } & 327 & 24 \\ \text { A069 } & 73 & 5 \\ \text { A064 } & 20 & 86 \\ \text { A068 } & 221 & 0 \\ \text { A065 } & 3 & 109 \\\ \text { A063 } & 5 & 350 \end{array} $$ a. If they do compete, do you expect the number \(x\) of O. tridens and the number \(y\) of \(O .\) lowei barnacles to be positively or negatively correlated? Explain. b. If you want to test the theory that the two types of barnacles compete for space by conducting a test of the null hypothesis "the population correlation coefficient \(\rho\) equals 0 ," what is your alternative hypothesis? c. Conduct the test in part \(b\) and state your conclusions.
You are given these data: $$ \begin{array}{l|llllll} x & 1 & 2 & 3 & 4 & 5 & 6 \\ \hline y & 7 & 5 & 5 & 3 & 2 & 0 \end{array} $$ a. Plot the six points on graph paper. b. Calculate the sample coefficient of correlation \(r\) and interpret. c. By what percentage was the sum of squares of deviations reduced by using the least-squares predictor \(\hat{y}=a+b x\) rather than \(\bar{y}\) as a predictor of \(y ?\)
Refer to Exercise \(12.8 .\) The data, along with the \(M S\) Excel analysis of variance table are reproduced below: $$ \begin{array}{l|lllllll} x & 1 & 2 & 3 & 4 & 5 & 6 \\ \hline y & 9.7 & 6.5 & 6.4 & 4.1 & 2.1 & 1.0 \end{array} $$ a. Do the data provide sufficient evidence to indicate that \(y\) and \(x\) are linearly related? Use the information in the printout to answer this question at the \(5 \%\) level of significance. b. Calculate the coefficient of determination \(r^{2}\). What information does this value give about the usefulness of the linear model?
The table below, a subset of the data given in Exercise 3.33 , shows the gestation time in days and the average longevity in years for a variety of mammals in captivity. $$ \begin{array}{lrr} & \text { Gestation } & \text { Avg Longevity } \\\ \text { Animal } & \text { (days) } & \text { (yrs) } \\ \hline \text { Baboon } & 187 & 20 \\ \text { Bear (black) } & 219 & 18 \\ \text { Bison } & 285 & 15 \\ \text { Cat (domestic) } & 63 & 12 \\ \text { Elk } & 250 & 15 \\\ \text { Fox (red) } & 52 & 7 \\ \text { Goat (domestic) } & 151 & 8 \\\ \text { Gorilla } & 258 & 20 \\ \text { Horse } & 330 & 20 \\ \text { Monkey (rhesus) } & 166 & 15 \\ \text { Mouse (meadow) } & 21 & 3 \\\ \text { Pig (domestic) } & 112 & 10 \\ \text { Puma } & 90 & 12 \\ \text { Sheep (domestic) } & 154 & 12 \\ \text { Wolf (maned) } & 63 & 5 \end{array} $$ a. If you want to estimate the average longevity of an animal based on its gestation time, which variable is the response variable and which is the independent predictor variable? b. Assume that there is a linear relationship between gestation time and longevity. Calculate the leastsquares regression line describing longevity as a linear function of gestation time. c. Plot the data points and the regression line. Does it appear that the line fits the data? d. Use the appropriate statistical tests and measures to explain the usefulness of the regression model for predicting longevity.
What diagnostic plot can you use to determine whether the assumption of equal variance has been violated? What should the plot look like when the variances are equal for all values of \(x ?\)
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