(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)=√(x+vn - 0x² +0,² Identify the next step in this rule from the options below. x-5-₂²_0₂² ₁ 2 VX-1 + 2 0₂ OV--1+%2 n1 na OV--1-%2 n1 2 Since standard deviation is the square root of variance, it follows that 01 √22-9/322 n₁ 0,² 0,² 01+02 Ox-√₂ Compute the estimated standard error (in MPa). (Round your answer to three decimal places.) MPa (c) Calculate a point estimate of the ratio a/a₂ of the two standard deviations. (Round your answer to three decimal places.) 4 (d) Suppose a single beam and a single cylinder are randomly selected. Calculate a point estimate (in MPa) of the variance of the difference X - Y between beam strength and cylinder strength. (Round your answer to two decimal places.) MPa2

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Can u help find the answer for b and explain d?
(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)=(x+v
= 0x² +0,²
Identify the next step in this rule from the options below.
OVX-5 đi t
0₁
VX-1+ °2²
7₂ ₂
OVX-1 + 2
1 7₂
7₂
OV--1-2
71 7₂
Since standard deviation is the square root of variance, it follows that
-√x-
V
Oox-
n₁
7₂
10₁ ²0₂ ²
Oox-₁₂
Oox-1
2
01 02
n₁ ₂
Compute the estimated standard error (in MPa). (Round your answer to three decimal places.)
MPa
(c) Calculate a point estimate of the ratio ₁/₂ of the two standard deviations. (Round your answer
three decimal places.)
4
(d) Suppose a single beam and a single cylinder are randomly selected. Calculate a point estimate (in MPa2) of the variance of the difference X - Y between beam strength and cylinder strength. (Round your answer to two decimal places.)
MPa2
Transcribed Image Text:(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)=(x+v = 0x² +0,² Identify the next step in this rule from the options below. OVX-5 đi t 0₁ VX-1+ °2² 7₂ ₂ OVX-1 + 2 1 7₂ 7₂ OV--1-2 71 7₂ Since standard deviation is the square root of variance, it follows that -√x- V Oox- n₁ 7₂ 10₁ ²0₂ ² Oox-₁₂ Oox-1 2 01 02 n₁ ₂ Compute the estimated standard error (in MPa). (Round your answer to three decimal places.) MPa (c) Calculate a point estimate of the ratio ₁/₂ of the two standard deviations. (Round your answer three decimal places.) 4 (d) Suppose a single beam and a single cylinder are randomly selected. Calculate a point estimate (in MPa2) of the variance of the difference X - Y between beam strength and cylinder strength. (Round your answer to two decimal places.) MPa2
Consider the accompanying data on flexural strength (MPa) for concrete beams of a certain type.
6.8 7.0 7.2 6.8
8.4 8.7 7.8 9.7 7.4 7.7 9.7 8.0 7.7 11.6
The data below give accompanying strength observations for cylinders.
5.1
O
7.2
7.3 6.3 8.1
6.5 5.8 7.8 7.1 7.2 9.2 6.6 8.3
7.2 8.1 7.4 8.5 8.9 9.8 9.7 14.1
O E(X-Y)=√E(X) - E(X)=H₁-H₂
O EX-- (EX-EM)²-1₂-1₂
O E(X)=E(X) - E()
=H₁-H₂
nm
E(X-Y)= E(X) - E(Y) = H₁ - 1₂
E(X-= nm (EX) - E() -μ₁-
1₂
6.5
***
7.0 8.5
12.6 11.4
7.0 6.3 7.9
Prior to obtaining data, denote the beam strengths by X₁, Xm and the cylinder strengths by Y₁, Y Suppose that the X's constitute a random sample from a distribution with mean , and standard deviation
o, and that the Y's form a random sample (independent of the X's) from another distribution with mean , and standard deviation a
%1
(a) Use rules of expected value to show that X - Y is an unbiased estimator of #₁ - 2.
11.3
11.8 10.7
9.0
Calculate the estimate (in MPa) for the given data. (Round your answer to three decimal places.)
-474
✓
MPa
Transcribed Image Text:Consider the accompanying data on flexural strength (MPa) for concrete beams of a certain type. 6.8 7.0 7.2 6.8 8.4 8.7 7.8 9.7 7.4 7.7 9.7 8.0 7.7 11.6 The data below give accompanying strength observations for cylinders. 5.1 O 7.2 7.3 6.3 8.1 6.5 5.8 7.8 7.1 7.2 9.2 6.6 8.3 7.2 8.1 7.4 8.5 8.9 9.8 9.7 14.1 O E(X-Y)=√E(X) - E(X)=H₁-H₂ O EX-- (EX-EM)²-1₂-1₂ O E(X)=E(X) - E() =H₁-H₂ nm E(X-Y)= E(X) - E(Y) = H₁ - 1₂ E(X-= nm (EX) - E() -μ₁- 1₂ 6.5 *** 7.0 8.5 12.6 11.4 7.0 6.3 7.9 Prior to obtaining data, denote the beam strengths by X₁, Xm and the cylinder strengths by Y₁, Y Suppose that the X's constitute a random sample from a distribution with mean , and standard deviation o, and that the Y's form a random sample (independent of the X's) from another distribution with mean , and standard deviation a %1 (a) Use rules of expected value to show that X - Y is an unbiased estimator of #₁ - 2. 11.3 11.8 10.7 9.0 Calculate the estimate (in MPa) for the given data. (Round your answer to three decimal places.) -474 ✓ MPa
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