hw9_solution

# hw9_solution - 10:26 PM C\Documents and Settings\Kevin...

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Unformatted text preview: 4/17/09 10:26 PM C:\Documents and Settings\Kevin Haas\My Documents\cla...\hw8_2.m 1 of 2 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % problem 8.2 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% clear clc %Input the speed x x=[40 9 100 50 15 65 25 60 95 60 30 125]; %Input the stopping distance y y=[15 2 40 15 4 25 5 25 30 24 8 45]; N=length(x); %Sort the values from lowest to highest [x ind]=sort(x); y=y(ind); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % Part (a) %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% figure(1) clf plot(x,y, 'x' , 'markersize' ,12, 'linewidth' ,2) xlabel( 'Speed (kph)' ) ylabel( 'Stopping distance (m)' ) grid on %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % Part (b) %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % Find the means and standard deviations xbar=mean(x); s_x=std(x); ybar=mean(y); s_y=std(y); %Find the regression coefficients xy=x.*y; x2=x.*x; beta=(sum(xy)-N*xbar*ybar)/(sum(x2)-N*xbar^2) alpha=ybar-beta*xbar %Regression values yprime yp=alpha+beta*x; %Plot the regression line figure(1) hold on plot(x,yp, 'r' , 'linewidth' ,2) %Find the conditional variance s2yx=1/(N-2)*sum((y-yp).^2); syx=sqrt(s2yx) %Find the correlation coefficient rho=beta*s_x/s_y %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % Part (c) %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %Find the critical value for 10% with 10 dof t_crit=1.8125; %Find the confidence interval 4/17/09 10:26 PM C:\Documents and Settings\Kevin Haas\My Documents\cla...\hw8_2.m 2 of 2 conf=t_crit*syx*sqrt(1/N+(x-xbar).^2/sum((x-xbar).^2)); %Plot the conf interval figure(1) hold on plot(x,yp+conf, 'k' ,x,yp-conf, 'k' , 'linewidth' ,1.5) legend( 'data' , 'yprime' , 'confidence' , 'location' , 'NW' ) 20 40 60 80 100 120 140-10 10 20 30 40 50 Speed (kph) Stopping distance (m) data yprime confidence 4/17/09 10:25 PM MATLAB Command Window 1 of 1 beta = 0.3863 alpha =-1.8611 syx = 2.8049 rho = 0.9819 >> 4/17/09 10:40 PM C:\Documents and Settings\Kevin Haas\My Documents\cla...\hw8_4.mC:\Documents and Settings\Kevin Haas\My Documents\cla....
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hw9_solution - 10:26 PM C\Documents and Settings\Kevin...

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