These consists confidence intervals, corelation,quality control.

3. To decide whether or not to purchase a new hand held laser scanner for use in inventory stock, test e conducted on the scanner currently in use and on the new scanner. The data are obtained on the imber of 7 - inch bar codes that can be scanned per second: New Old n1 = 61 n1 = 61 X1 = 40 X1 = 29 $ = 24.9 $3 = 22.7 i) Test Ho:07 = oz at the a = 0.2 level to be sure that pooling is appropriate ii) Find s? iii) Find a 90% confidence interval on 1 - #2 iv) Does the new laser appear to read more bar codes per second on average? Explain 4. A study is conducted to determine the effect of acid rain and other industrial pollutants on lake water. indom samples are drawn from 10 lakes in a heavily industrialized area and from the eight lakes in a imitive forested area. These data are obtained on the pH of the water: dustrial area (1) Primitive area (P) 7.0 7.0 6.8 2 6.5 6.9 7.1 6.6 6.7 7.0 5.5 7.1 7.2 7.3 the a = .025 level, can we claim that the pH of water in the industrialized area tends to be lower than at in primitive area? 5) Consider the following observations on the independent variable X and the dependent variable Y: y x y 5.0 100 6.7 4.7 115 4.2 4.5 110 5.5 3.2 105 6.4 2.0 105 6.8 10 6.5 100 7.2 6.0 130 2.0 5.5 125 2.9 5.2 120 3.8 a) Plot a scatter diagram of the data b) Does it appear reasonable that a linear regression could be used for these data c) Sketch, a linear regression line on the scatter diagram in part (a) d) Fit a linear regression to the data and estimate the regression coefficients by solving normal equations e) Find the residuals et = y - >, in each case, and verify that, apart from round - off error, the residuals sum to O