(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-7)= v(x+v(n = 0,² +0,² Identify the next step in this rule from the options below. 2 0 x-5-² X-5-02-02 --- --- Since standard deviation is the square root of variance, it follows that 0₂

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(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) = V(X) +v(n)
= 0x² +0,²
Identify the next step in this rule from the options below.
2
2
OV(X-=°1²
01 +
OV(X-1²-2²
=
0₁ 7₂
OV(X) = 1 + 2
n₁ 7₂
Ov(x)=01_%2
n₁
7₂
Since standard deviation is the square root of variance, it follows that
V(X-ň)
ºx-Y=V
7₁ 7₂
2
2
Oox - y = √
Oox-Y
⁰1
Oox-y= 7₁ 7₂
2
Oºx-= V
01+02
7₁ 7₂
R²
+
2
01-02
7₁ 7₂
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 to three decimal places.)
(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) = V(X) +v(n) = 0x² +0,² Identify the next step in this rule from the options below. 2 2 OV(X-=°1² 01 + OV(X-1²-2² = 0₁ 7₂ OV(X) = 1 + 2 n₁ 7₂ Ov(x)=01_%2 n₁ 7₂ Since standard deviation is the square root of variance, it follows that V(X-ň) ºx-Y=V 7₁ 7₂ 2 2 Oox - y = √ Oox-Y ⁰1 Oox-y= 7₁ 7₂ 2 Oºx-= V 01+02 7₁ 7₂ R² + 2 01-02 7₁ 7₂ 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 to three decimal places.) (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.
5.3 7.2 7.3 6.3 8.1 6.8 7.0 7.4
8.6 8.7 7.8 9.7 7.4 7.7 9.7 8.0 7.7 11.6 11.3 11.8 10.7
The data below give accompanying strength observations for cylinders.
6.7 5.8 7.8 7.1 7.2
7.2 8.1 7.4 8.5 8.9
Calculate the estimate (in MPa) for the
MPa
○ E(X - = (EX) - E()² =
= H₂ - H₂
O
E(X)=√E(X) – E(Y) = µ₁ −μ₂
-= H₂-H₂
O E(X)=E(X) - E(X)
nm
○ E(X)= nm (EX) - E(¯)-
= H₁ - H₂
9.2 6.6 8.3
Ov(x-) = 1 -.
0₁
Prior to obtaining data, denote the beam strengths by X₁, X and the cylinder strengths by Y₁, -, Y. Suppose that the X,'s constitute random sample from a distribution with mean μ, and standard deviation, and that the Y's form a random sample (independent of the X;'s) from another distribution with mean ₂ and standard deviation ₂2.
(a) Use rules of expected value to show that X - Y is an unbiased estimator of μ₁ - ₂
O E(X)=E(X) - E(X) = μ₁₂-1²₂
7₂
6.8 6.5
9.8 9.7 14.1 12.6 11.0
Identify the next step in this rule from the options below.
O V(x->) =
0₁² +
7₁
Ov(x)=1+%2
n₁
OV(X) = 10₂
M₁ 7₂
data. (Round
7.0 8.1
7.0
6.3 7.9 9.0
(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) = V(X) + V(5)
= 0x² +0₂²
nswer to three decimal places.)
Transcribed Image Text:Consider the accompanying data on flexural strength (MPa) for concrete beams of a certain type. 5.3 7.2 7.3 6.3 8.1 6.8 7.0 7.4 8.6 8.7 7.8 9.7 7.4 7.7 9.7 8.0 7.7 11.6 11.3 11.8 10.7 The data below give accompanying strength observations for cylinders. 6.7 5.8 7.8 7.1 7.2 7.2 8.1 7.4 8.5 8.9 Calculate the estimate (in MPa) for the MPa ○ E(X - = (EX) - E()² = = H₂ - H₂ O E(X)=√E(X) – E(Y) = µ₁ −μ₂ -= H₂-H₂ O E(X)=E(X) - E(X) nm ○ E(X)= nm (EX) - E(¯)- = H₁ - H₂ 9.2 6.6 8.3 Ov(x-) = 1 -. 0₁ Prior to obtaining data, denote the beam strengths by X₁, X and the cylinder strengths by Y₁, -, Y. Suppose that the X,'s constitute random sample from a distribution with mean μ, and standard deviation, and that the Y's form a random sample (independent of the X;'s) from another distribution with mean ₂ and standard deviation ₂2. (a) Use rules of expected value to show that X - Y is an unbiased estimator of μ₁ - ₂ O E(X)=E(X) - E(X) = μ₁₂-1²₂ 7₂ 6.8 6.5 9.8 9.7 14.1 12.6 11.0 Identify the next step in this rule from the options below. O V(x->) = 0₁² + 7₁ Ov(x)=1+%2 n₁ OV(X) = 10₂ M₁ 7₂ data. (Round 7.0 8.1 7.0 6.3 7.9 9.0 (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) = V(X) + V(5) = 0x² +0₂² nswer to three decimal places.)
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