8.1 as a mixed number

The tensile strength of stainless steel produced by a plant has been stable for a long time with a mean of 72 kg/mm2 and a stand

Elanso [62]

Answer:

95% confidence interval for the mean of tensile strength after the machine was adjusted is [73.68 kg/mm2 , 74.88 kg/mm2].

Yes, this data suggest that the tensile strength was changed after the adjustment.

Step-by-step explanation:

We are given that the tensile strength of stainless steel produced by a plant has been stable for a long time with a mean of 72 kg/mm 2 and a standard deviation of 2.15.

A machine was recently adjusted and a sample of 50 items were taken to determine if the mean tensile strength has changed. The mean of this sample is 74.28. Assume that the standard deviation did not change because of the adjustment to the machine.

Firstly, the pivotal quantity for 95% confidence interval for the population mean is given by;

P.Q. = $\frac{\bar X-\mu}{\frac{\sigma}{\sqrt{n} } }$ ~ N(0,1)

where, $\bar X$ = sample mean strength of 50 items = 74.28

$\sigma$ = population standard deviation = 2.15

n = sample of items = 50

$\mu$ = population mean tensile strength after machine was adjusted

Here for constructing 95% confidence interval we have used One-sample z test statistics as we know about population standard deviation.

So, 95% confidence interval for the population mean, $\mu$ is ;

P(-1.96 < N(0,1) < 1.96) = 0.95 {As the critical value of z at 2.5% level of

significance are -1.96 & 1.96}

P(-1.96 < $\frac{\bar X-\mu}{\frac{\sigma}{\sqrt{n} } }$ < 1.96) = 0.95

P( $-1.96 \times {\frac{\sigma}{\sqrt{n} } }$ < ${\bar X-\mu}$ < $1.96 \times {\frac{\sigma}{\sqrt{n} } }$ ) = 0.95

P( $\bar X-1.96 \times {\frac{\sigma}{\sqrt{n} } }$ < $\mu$ < $\bar X+1.96 \times {\frac{\sigma}{\sqrt{n} } }$ ) = 0.95

95% confidence interval for $\mu$ = [ $\bar X-1.96 \times {\frac{\sigma}{\sqrt{n} } }$ , $\bar X+1.96 \times {\frac{\sigma}{\sqrt{n} } }$ ]

= [ $74.28-1.96 \times {\frac{2.15}{\sqrt{50} } }$ , $74.28+1.96 \times {\frac{2.15}{\sqrt{50} } }$ ]

= [73.68 kg/mm2 , 74.88 kg/mm2]

Therefore, 95% confidence interval for the mean of tensile strength after the machine was adjusted is [73.68 kg/mm2 , 74.88 kg/mm2].

Yes, this data suggest that the tensile strength was changed after the adjustment as earlier the mean tensile strength was 72 kg/mm2 and now the mean strength lies between 73.68 kg/mm2 and 74.88 kg/mm2 after adjustment.

8 0

3 years ago

Solve the equation for x. 2(x-2) + 6 = 2

Tpy6a [65]

Answer:

x=0

Step-by-step explanation:

2x-4+6=2

2x+2=2

2x=0

x=0

6 0

3 years ago

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HELP ASAP!!

garri49 [273]

I'm pretty sure it would be x - y + 1 = 0 because if you plug in one of the coordinates into each equation, this is the only one that works.

y - x + 1 = 0
2 - 1 + 1 = 0
2 = 0 not correct

x - y + 1 = 0
1 - 2 + 1 = 0
0 = 0 correct

-x - y + 1 = 0
-1 - 2 + 1 = 0
-2 = 0 not correct

4 0

3 years ago

The Ford family decides they want to go see a movie at the local movie theater. The family consists of two adults, and five chil

Brrunno [24]

Ford Family consists of:

a) 2 adults

The price of ticket for each adult is $18.55. This can be approximated to $19 if we round it to nearest dollar. So the price of ticket for 2 adults will be 2 x 19 = $38

b) 3 children between ages 2 and 10.

Ticket for each child between ages 2 - 10 is $12.59 which can be approximated to $13. So ticket price for 3 children will be 3 x 13 = $39

c) 2 children below the age of 2.

Ticket price for each child is $6.54 which can approximated as $7. So ticket price for 2 children will be 2 x 7 = $14

The estimated total amount due on the family equals = 38 + 39 + 14 = $91

In each of the 3 cases we rounded up the values. So this means the actual amount must be slightly lesser than $91. The actual bill was $87.95 which is close to $91 and lesser than it. Hence we can conclude that $87.95 is the correct amount due for Ford Family.

3 0

3 years ago

What is 2 plus 2

kotegsom [21]

Answer:

4

Step-by-step explanation:

3 0

3 years ago

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8.1 as a mixed number​

8.1 as a mixed number