Example 1 Two doctors recommend treating colds with two different methods. The results (number of days of the treatment) are x1={5 8 7 8 4 5 5 6 9 3 5 8 6 8 7 5 8 5 7 5 6 8 4 7 7 5 6}; x2={3 4 9 5 4 9 9 8 3 3 5 3 6 4 5 6 2 2 3 4 2 3}; Test equality of the methods. Normality cannot be assumed. Results pv=0.005 ------------------------------------------------------------- Example 2 At certain process we have measured the data xi = {5 12 20 26 29 38 40 45}; yi = {9 7 12 12 27 35 44 76}; Perform the 3rd order polynomial regression and the exponential regression. Using prediction errors decide which type of regression is better. Results SE_p = 5.98 SE_e = 0.32 ------------------------------------------------------------- Example 3 We are going to test if the tire removal on left and right sides of the front wheels of cars is equal. The measured values are 'xL' a 'xP'. Test at the level 0.05. xL = {1.8 1.0 2.2 0.9 1.5}; xP = {1.5 1.1 2.0 1.1 1.4}; Results pv = 0.55 ------------------------------------------------------------- Example 4 To learn the accuracy of a method for measuring the volume of manganese in the steel, we performed independent measurements of several variances. We would like to know the border for which it holds that only 5% of possibly measured variances will be greater than this border. The measured values are x = {4.3 2.9 5.1 3.3 2.7 4.8 3.6}; Results The border is 4.5 ------------------------------------------------------------- Example 5 A factory produces some products whose weight must be constant. For the production it uses four machines. A sample of products has been taken from all machines to test equality of the product weights. The measured values are x1={39.4 34.8 35.6 35.1 35.8}; x2={34.4 34.2 35.1 31.1 32.5 33.8}; x3={30.2 35.1 34.2 36.3 30.8 35.6 35.2}; x4={39.1 34.3 38.6 34.5 36.4 36.1}; Test the equality. The data are not normally distributed. Results pv = 0.033 ------------------------------------------------------------- Example 6 At a crossroads we have written down numbers of passing cars. The measured data are: d = 15 10 20 35 10 50 - length of monitoring and x = 71 56 98 121 44 271 - number of cars At the level 0.05 test the hypothesis that the cars go uniformly. Results pv = 0.0013 ------------------------------------------------------------- Example 7 The accuracy of setting of certain machine can be verified according to the variance of the products. If the variance is greater then the level 90, it is necessary to perform new setting. A data sample has been meaasured with values mx = {100 95 100 110 105 110 125 90 100 120 110}; On the level 0.05 test if it is necessary to set the machine. Test on the level al = 0.05; Results pv = 0.28 ------------------------------------------------------------- Example 8 Tree inspectors are to evaluate functionality of five fast food stands. Each inspector evaluates each stand. The result is the table Tab: rows correspond to inspectors, columns columns to stands. Evaluation is 1,2,..,10. 10 is the best. Test if the quality of the stans is equal. Tab={{10 8 3 9 7} {8 7 5 9 10} {8 9 5 7 6}} Results pv = 0.155 ------------------------------------------------------------- Example 9 A harmful substance has leaked into the water tank. A neutralizing agent was used and the concentration of the pollutant was measured at time points 'xi' . The time instances 'xi' and measured concentrations 'yi' are xi = {5 12 20 26 29 38 65 126}; yi = {19 17 18 17 17 15 14 7}; Compute the correlation coefficient of linear regression and conclude about its suitability. If suitable, estimate when the concentration will be zero. Results Correletion coefficient r = -0.9832531 Parameters p = -0.0948295xi + 19.305033 Zero concentration at x_zero x_zero = 203.57626 ------------------------------------------------------------- Example 10 We monitor three machines. Randomly, we measure their productions per hour 'x1', 'x2' and 'x3. At the level 0.05, test the equality of their production if normality of data is assumed. x1 = {53 55 49 58 52 61 56 55}; x2 = {49 56 52 45 51 56 44 51}; x3 = {52 53 52 54 55 53 53 52}; Results pv = 0.0541908 ------------------------------------------------------------- Example 11 At certain process we have measured the data x1i = {15 12 11 9 9 8 5 3}'; x2i = {3 9 5 11 28 14 32 58}'; yi = {9 7 22 12 27 31 44 36}'; Perform multivariate linear regression and test its suitability. Results pv = 0.045: ------------------------------------------------------------- Example 12 A connection between color of eyes and hair has been investigated. In a collected data sample we obtained the following frequencies eyes \ hair light brown dark blue {90 75 55} gray {96 136 88} brown {108 135 119} At the level 0.05 test the hypothesis that the color of eyes and hair are independent. Results pv = 0.017 ------------------------------------------------------------- Example 13 At the motorway with recommended speed 80 km/h we monitored the speeds of passing cars and obtained data x = {78 86 65 92 83 92 85 66 42 82 99 92 75 81 66 76 89 76 97 76 75 56 76 78 96 77 86 79 86 93}; Test H0: the ratio of drivers that exceed the recommended speed by more than 3 km/h is not greater then 0.2. Test at alpha = 0.05. Results pv=0.033 -------------------------------------------------------------