Empirical cumulative distribution function (cdf) plot |
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Open Live Script Perform the one-sample Kolmogorov-Smirnov test by using kstest. Confirm the test decision by visually comparing the empirical cumulative distribution function (cdf) to the standard normal cdf. Load the examgrades data set. Create a vector containing the first column of the exam grade data. load examgrades test1 = grades(:,1);Test the null hypothesis that the data comes from a normal distribution with a mean of 75 and a standard deviation of 10. Use these parameters to center and scale each element of the data vector, because kstest tests for a standard normal distribution by default. x = (test1-75)/10; h = kstest(x)h = logical 0The returned value of h = 0 indicates that kstest fails to reject the null hypothesis at the default 5% significance level. Plot the empirical cdf and the standard normal cdf for a visual comparison. cdfplot(x) hold on x_values = linspace(min(x),max(x)); plot(x_values,normcdf(x_values,0,1),'r-') legend('Empirical CDF','Standard Normal CDF','Location','best')The figure shows the similarity between the empirical cdf of the centered and scaled data vector and the cdf of the standard normal distribution. |
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