This homework question is giving me a tough time as I have tried the previous result and got wrong and the second submission is also wrong.

2nd submission below:

Calculate the estimate for the given data. (Round your answer to three decimal places.) - (b) Use rules of variance to obtain an expression for the variance and standard deviation (standard error) of the estimator in part (a). WY 7) = w?) + 1/07) = 6X2 + W2 II + I3 X II + I3 M X Compute the estimated standard error. (Round your answer to three decimal places.) - (c) Calculate a point estimate of the ratio 01/02 of the two standard deviations. (Round your answer to three decimal places.) -.I Consider the accompanying data on flexural strength (MPa) for concrete beams of a certain type. 5.0 7.2 7.3 6.3 8.1 6.8 7.0 7.5 6.8 6.5 7.0 6.3 7.9 9.0 8.9 8.7 7.8 9.7 7.4 7.7 9.7 7.8 7.7 11.6 11.3 11.8 10.7 The data below give accompanying strength observations for cylinders. 6.8 5.8 7.8 7.1 7.2 9.2 6.6 8.3 7.0 8.7 7.4 8.1 7.4 8.5 8.9 9.8 9.7 14.1 12.6 11.3 Prior to obtaining data, denote the beam strengths by X], . . ., X, and the cylinder strengths by Y, . . ., Y,. Suppose that the X's constitute a random sample from a distribution with mean #, and standard deviation , and that the Y's form a random sample (independent of the X's) from another distribution with mean M2 and standard deviation o2. (a) Use rules of expected value to show that X - Y is an unbiased estimator of #1 - #2. O E( X - Y) = E(X) - E(n) = M1 - H2 O E( X - n) = ( E ( x ) - E ( n ) = M 1 - H 2 E( X - n) = nm(E(x) - E(n) = M1 - H 2 O E( X - n) = VE(X) - E( = 1 1 - 12 O E( X - n) = = ( X ) - Em = 1 1 - H2 nm Calculate the estimate for the given data. (Round your answer to three decimal places.) -0.485 MPa (b) Use rules of variance to obtain an expression for the variance and standard deviation (standard error) of the estimator in part (a). V ( x - 1) = V( x ) + vin = oxtoy2 5 2 82.3655 19 n 1 OX - y = VV( x - n 82.3655 19 n1 Compute the estimated standard error. (Round your answer to three decimal places.) 0.572 MPa (c) Calculate a point estimate of the ratio 61/62 of the two standard deviations. (Round your answer to three decimal places.) 0.827 (d) Suppose a single beam and a single cylinder are randomly selected. Calculate a point estimate of the variance of the difference X - Y between beam strength and cylinder strength. (Round your answer to two decimal places.) 7.302 MPa