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Suppose the expected tensile strength of type-A steel is 103 ksi and the standard deviation of tensile strength is 7 ksi. For ty

ExtremeBDS [4]

Answer:

a

i So the approximate distribution of $\= X$ is $\mu_{\= X} =103$ and $\sigma_{\= X} = 0.783$

ii So the approximate distribution of $\= Y$ is $\mu_{\= Y} =105$ and $\sigma_{\= Y} = 0.645$

b

the approximate distribution of $\=X - \= Y$ is $E (\= X - \= Y) = -2$ and $\sigma_{\= X - \=Y}=1.029$

Here we can see that the mean of the approximate distribution is negative which tell us that this negative value of the data for $\=X - \= Y$ sample are more and their frequency occurrence is higher than the positive values

c

the value of $P(-1 \le \=X - \= Y \le 1)$ is $= -0.1639$

Step-by-step explanation:

From the question we are given that

The expected tensile strength of the type A steel is $\mu_A = 103 ksi$

The standard deviation of type A steel is $\sigma_A = 7ksi$

The expected tensile strength of the type B steel is $\mu_B = 105\ ksi$

The standard deviation of type B steel is $\sigma_B = 5 \ ksi$

Also the assumptions are

Let $\= X$ be the sample average tensile strength of a random sample of 80 type-A specimens

Here $n_a =80$

Let $\= Y$ be the sample average tensile strength of a random sample of 60 type-B specimens.

Here $n_b = 60$

Let the sampling distribution of the mean be

$\mu _ {\= X} = \mu$

$=103$

Let the sampling distribution of the standard deviation be

$\sigma _{\= X} = \frac{\sigma }{\sqrt{n_a} }$

$= \frac{7}{\sqrt{80} }$

$=0.783$

So What this mean is that the approximate distribution of $\= X$ is $\mu_{\= X} =103$ and $\sigma_{\= X} = 0.783$

For $\= Y$

The sampling distribution of the sample mean is

$\mu_{\= Y} = \mu$

$= 105$

The sampling distribution of the standard deviation is

$\sigma _{\= Y} = \frac{\sigma }{\sqrt{n_b} }$

$= \frac{5}{\sqrt{60} }$

$= 0.645$

So What this mean is that the approximate distribution of $\= Y$ is $\mu_{\= Y} =105$ and $\sigma_{\= Y} = 0.645$

Now to obtain the approximate distribution for $\=X - \= Y$

$E (\= X - \= Y) = E (\= X) - E(\= Y)$

$= \mu_{\= X} - \mu_{\= Y}$

$= 103 -105$

$= -2$

The standard deviation of $\=X - \= Y$ is

$\sigma_{\= X - \=Y} = \sqrt{\sigma_{\= X}^2 - \sigma_{\= Y}^2}$

$= \sqrt{(0.783)^2 + (0.645)^2}$

$=1.029$

Now to find the value of $P(-1 \le \=X - \= Y \le 1)$

Let us assume that $F = \= X - \= Y$

$P(-1 \le F \le 1)$ $= P [\frac{-1 -E (F)}{\sigma_F} \le Z \le \frac{1-E(F)}{\sigma_F} ]$

$= P[\frac{-1-(-2)}{1.029} \le Z \le \frac{1-(-2)}{1.029} ]$

$= P[0.972 \le Z \le 2.95]$

$= P(Z \le 0.972) - P(Z \le 2.95)$

Using the z-table to obtain their z-score

$= 0.8345 - 0.9984$

$= -0.1639$

3 0

2 years ago

• footballs – There are 8 footballs.

inna [77]

Answer:

8 futballs

basketballs 18

beisballs 36

softballs 24

Step-by-step explanation:

dos mas del doble (2) de balones de fut = 8x2 = 16, 16+2 = 18

cuatro menos de 5 veces las pelotas de fut = 8x5 = 40, 40-4 = 36

seis mas de la mitad de beis = 36/2 = 18, 18+6 = 24

LISTO

7 0

2 years ago

Which expression is equivalent to the following: *<br> 20x+9y

anzhelika [568]

Answer:

B. 5(4x+2y)-y

Step-by-step explanation:

Bring the 5 over and multiply

5×4 = 20 + x

=20x (thats the beginning of the expression)

5×2 = 10

10y - y = 9 because the - y is basically telling you to get rid of one of the y values so 10 - 1 = 9y

7 0

2 years ago

True or false if you know the area and length of a rectangle you can find its width ?

a_sh-v [17]

True. The formula for the area of a rectangle is length multiplied by width. Therefore, we can find the width by dividing the area by the length through Division Property of Equality.

4 0

3 years ago

Work out the perimeter of the triangle when the sides are : 3x-5 2x 19-x

mr Goodwill [35]

Answer:

4x + 14

Step-by-step explanation:

The perimeter of the triangle is equal to the sum of its three sides.

The sides of the triangle are 3x-5, 2x, and 19-x.

Calculate their sum.

3x - 5 + 2x + 19 - x

Rearrange.

3x + 2x - x + 19 - 5

Add or subtract like terms.

4x + 14

The perimeter of the triangle is 4x + 14.

5 0

3 years ago

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