Rockwell hardness of pins of a certain type is known to have a mean value of 50 and a standard deviation of 1.2.a. If the distribution is normal, what is the probability that the sample mean hardness for a random sample of 9 pins is at least 51?b. Without assuming population normality, what is the (approximate) probability that the sample mean hardness for a random sample of 40 pins is at least 51?

Answers

Answer 1

Answer:

a

 [tex]P(\= X \ge 51 ) =0.0062[/tex]

b

[tex]P(\= X \ge 51 ) = 0[/tex]

Step-by-step explanation:

From the question we are told that

The mean value is [tex]\mu = 50[/tex]

The standard deviation is  [tex]\sigma = 1.2[/tex]

Considering question a

The sample size is  n = 9

Generally the standard error of the mean is mathematically represented as

      [tex]\sigma_x = \frac{\sigma }{\sqrt{n} }[/tex]

=>   [tex]\sigma_x = \frac{ 1.2 }{\sqrt{9} }[/tex]

=>  [tex]\sigma_x = 0.4[/tex]

Generally the probability that the sample mean hardness for a random sample of 9 pins is at least 51 is mathematically represented as

      [tex]P(\= X \ge 51 ) = P( \frac{\= X - \mu }{\sigma_{x}} \ge \frac{51 - 50 }{0.4 } )[/tex]

[tex]\frac{\= X -\mu}{\sigma }  =  Z (The  \ standardized \  value\  of  \ \= X )[/tex]

     [tex]P(\= X \ge 51 ) = P( Z \ge 2.5 )[/tex]

=>   [tex]P(\= X \ge 51 ) =1- P( Z < 2.5 )[/tex]

From the z table  the area under the normal curve to the left corresponding to  2.5  is

    [tex]P( Z < 2.5 ) = 0.99379[/tex]

=> [tex]P(\= X \ge 51 ) =1-0.99379[/tex]

=> [tex]P(\= X \ge 51 ) =0.0062[/tex]

Considering question b

The sample size is  n = 40

   Generally the standard error of the mean is mathematically represented as

      [tex]\sigma_x = \frac{\sigma }{\sqrt{n} }[/tex]

=>   [tex]\sigma_x = \frac{ 1.2 }{\sqrt{40} }[/tex]

=>  [tex]\sigma_x = 0.1897[/tex]

Generally the (approximate) probability that the sample mean hardness for a random sample of 40 pins is at least 51 is mathematically represented as  

       [tex]P(\= X \ge 51 ) = P( \frac{\= X - \mu }{\sigma_x} \ge \frac{51 - 50 }{0.1897 } )[/tex]

=> [tex]P(\= X \ge 51 ) = P(Z \ge 5.2715 )[/tex]

=>  [tex]P(\= X \ge 51 ) = 1- P(Z < 5.2715 )[/tex]

From the z table  the area under the normal curve to the left corresponding to  5.2715 and

=>  [tex]P(Z < 5.2715 ) = 1[/tex]

So

   [tex]P(\= X \ge 51 ) = 1- 1[/tex]

=> [tex]P(\= X \ge 51 ) = 0[/tex]

Answer 2

Using the normal distribution and the central limit theorem, we have that there is a:

a) 0.0062 = 0.62% probability that the sample mean hardness for a random sample of 9 pins is at least 51.

b) 0% approximate probability that the sample mean hardness for a random sample of 40 pins is at least 51.

In a normal distribution with mean and standard deviation , the z-score of a measure X is given by:

[tex]Z = \frac{X - \mu}{\sigma}[/tex]

It measures how many standard deviations the measure is from the mean.  After finding the z-score, we look at the z-score table and find the p-value associated with this z-score, which is the percentile of X. By the Central Limit Theorem, the sampling distribution of sample means of size n has standard deviation [tex]s = \frac{\sigma}{\sqrt{n}}[/tex].

In this problem:

Mean of 50, hence [tex]\mu = 50[/tex]Standard deviation of 1.2, hence [tex]\sigma = 1.2[/tex]Sample of 9, hence [tex]n = 9, s = \frac{1.2}{\sqrt{9}} = 0.4[/tex].

Item a:

The probability is 1 subtracted by the p-value of Z when X = 51, hence:

[tex]Z = \frac{X - \mu}{\sigma}[/tex]

By the Central Limit Theorem

[tex]Z = \frac{X - \mu}{s}[/tex]

[tex]Z = \frac{51 - 50}{0.4}[/tex]

[tex]Z = 2.5[/tex]

[tex]Z = 2.5[/tex] has a p-value of 0.9938.

1 - 0.9938 = 0.0062

There is a 0.0062 = 0.62% probability that the sample mean hardness for a random sample of 9 pins is at least 51.

Item b:

Even though the distribution is not normal, the sample size is of [tex]n = 40 > 30[/tex], hence the Central Limit Theorem can be applied.

[tex]s = \frac{1.2}{\sqrt{40}} = 0.19[/tex]

[tex]Z = \frac{X - \mu}{s}[/tex]

[tex]Z = \frac{51 - 50}{0.19}[/tex]

[tex]Z = 5.26[/tex]

[tex]Z = 5.26[/tex] has a p-value of 1.

1 - 1 = 0

0% approximate probability that the sample mean hardness for a random sample of 40 pins is at least 51.

A similar problem is given at https://brainly.com/question/24663213


Related Questions

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Step-by-step explanation:

the 3rd makes 1 whole

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Step-by-step explanation:

Change 4/(2/3) to 4(3)/2.
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Answer:

1747

Step-by-step explanation:

3000 - 1253 = 1747

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Answers

Answer: c, but I’m not totally sure

Step-by-step explanation:

The amount of gasoline G sold each month to customers at Bob's Exxon station in downtown Navasota is a random variable. This random variable G can be described as having a normal distribution with mean 2500 gallons and a standard deviation of 250 gallons (and there is no seasonal variation in sales). Exxon will give Bob an all-expense paid trip to College Station, including a free dinner at Burger King, if his station pumps more than 3000 gallons in any one month.


Required:

What is the probability that Bob will win that wonderful trip on the basis of his gasoline sales this month?

Answers

Answer:

The probability is [tex]0.0228[/tex]

Step-by-step explanation:

Let's start by defining the random variable [tex]G[/tex] as :

[tex]G:[/tex] '' The amount of gasoline sold each month to customers at Bob's Exxon station in downtown Navasota ''

Therefore, if [tex]X[/tex] is a continuous random variable that has a normal distribution, we write [tex]X[/tex] ~ [tex]N[/tex] ( μ , σ )

Where ''μ'' is the mean and ''σ'' is the standard deviation.

For the random variable [tex]G[/tex] we write :

[tex]G[/tex] ~ [tex]N(2500,250)[/tex]

We need to find [tex]P(G>3000)[/tex]

In order to calculate this, we are going to standardize the variable. This means, finding the equivalent probability in a normal random variable

[tex]Z[/tex] ~ [tex]N(0,1)[/tex]

We perform this because the random variable [tex]Z[/tex] ~ [tex]N(0,1)[/tex] is tabulated in any book or either you can find the table on Internet.

To standardize the variable we need to subtract the mean and then divide by the standard deviation ⇒

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Because (G - μ) / σ  ~ [tex]Z[/tex]

Finally, [tex]P(G>3000)=P(Z>2)[/tex] ⇒ [tex]P(Z>2)=1-P(Z\leq 2)[/tex] = 1 - Φ(2)

Where '' Ф(x) = [tex]P(X\leq x)[/tex] '' represents the cumulative function of [tex]Z[/tex]

Looking for  Φ(2) in any table,

[tex]P(G>3000)=P(Z>2)=1-P(Z\leq 2)=1-0.9772=0.0228[/tex] ≅ %2.28

We found out that the probability is [tex]0.0228[/tex]

What is the slope of the line going through the points (2,5) and (-4,-1)?

Answers

Answer: The answer is 1.

Step-by-step explanation: The entered points belong to an increasing, linear function.

Equation: y = 1x + 3.

The slope is 1.

Use the formula m=y2-y1/x2-x1 to plug in the x and y values and subtract.

-1-5/-4-2=-6/-6

-6/-6 simplifies to 1.

Hope this helps!

A company weighs 1,096 boxes of cereal and finds that 12.5% of them weighed less than one pound. Which of
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Answers

Answer:

500

Step-by-step explanation:

HELP ASAP! What are the slope and y-intercept of the linear function that is represented by the table?
A. The slope ls -2, and the y-intercept is 6.
B. The slope ls -2, and the y-intercept is 12.
C. The slope is 2, and the y-intercept is 6.
D. The slope is 2, and the y-intercept is 12.​

Answers

Answer:

A

Step-by-step explanation:

Answer:

Step-by-step explanation:

Use two points and find slope initially so,

(-3,18) (0,12)

18-12=6   ,  -3-0= -3

so the slope is 6/-3 = -2 so by this answer is either a or b .

further apply y =mx + c as it linear to find c

y= -2x + c

0 = -2x6 + c

c = 12

so slope is -2 , c is 12

Raise to the power:
c
(–3y)4

Answers

Answer:

3^4 x y^4

Step-by-step explanation:

Helopppppp pleaseeeeeee

Answers

THE WORKKK AND ANSWER ( Brainliest Answer Will be appreciated:D)

Answer:

x=2, x=1/2, x=-2/3

Step-by-step explanation:

First factor and get (x-2)(2x-1)(3x+2)=0

Then you set each of these parentheses individually equal to 0. x-2=0, 2x-1=0, 3x+2=0. Then you just simplify these to get your final answer that I showed above.

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Answers

Answer:

This is a decrease

Step-by-step explanation:

3.33%

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Answers

Answer:

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Step-by-step explanation:

Set up a proportion.

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3.29/p = 9.25 ounces/(1 ounce)

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p = 3.29 ÷ 9.25

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Answers

Answer:

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Step-by-step explanation:

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Answers

Answer:

34% of scores should fall between your score and the mean.

Step-by-step explanation:

Let X denote the score.

It is provided that X follows a normal distribution with mean 110 and standard deviation 15.

A students score, x = 95.

Compute the probability of scores that should fall between the student's score and the mean as follows:

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Answers

Answer:

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Step-by-step explanation:

the opposite of 20 is -20

Answer:

im going to edit it when i finish the quiz

Step-by-step explanation:

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Answers

Answer:

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Step-by-step explanation:

23*11 which is 253.

Hope this helps plz mark brainliest :D

Answer is :253

Please mark me as Brainliest ......

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ANSWER FOR BRAINLIEST

Answers

Hi there!

[tex]\large\boxed{182}[/tex]

Equation:

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Evaluate by plugging in -6 for a:

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Select the correct answer.
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Answers

Answer:

He drove the rest of the trip at 30 miles per hour

Step-by-step explanation:

The rule of the distance is D = v × t, where

v is the speedt is the time

∵ It is 170 miles from Bruce's house to the city where his brother lives

D = 170 miles

∵ He drove for 2 hours at 55 miles per  hour

t1 = 2 hours and v1 = 55 miles/hour

→ By using the rule above find the distance of this part of his trip

D1 = 55 × 2 = 110 miles

∵ The rest of the trip took 2 hours

t2 = 2 hours

∵ D = D1 + D2

→ Substitute the values of D and D1 to find D2

170 = 110 + D2

→ Subtract 110 from both sides to find D2

∴ 60 = D2

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→ Divide both sides by 2

∴ 30 = v2

v2 = 30 miles/hour

He drove the rest of the trip at 30 miles per hour

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Answers

Answer:

<1=<2Being vertical angles

<2+<3=90° Being complementary angle

m<3=56

now

<2+<3=90

<2=90-56

<2=34

:.<1=34°


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Answers

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Answers

Answer:

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Hoped this helped:)

Step-by-step explanation:

Answer:

6,232 rounded is 6,200

490 rounded is 500

23,058 rounded is 23,100

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Answers

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Step-by-step explanation:

6 is the ones place. 0 is the tenths place. 5 is the hundredths place.

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Answers

Answer:

17

Step-by-step explanation:

this is an isosceles triangle so AB = AC

2x-8 = x + 9

x -8 = 9

x = 17

so CB = 17

Hi can you please tell me the answe to this question its due in a few mins. Thank you so much!!​

Answers

Answer:

LNO I BELIEVE

Step-by-step explanation:

IT MAKES THE SAME SHAPE THAT NMO MAKES

Can someone help me solve this

Answers

Answer:

sin x = -5/13

csc x = -13/5

sec x = 13/12

cot x = -12/5

tan x = -5/12

Step-by-step explanation:

**x is in quadrant iv because 3pi/2<x<2pi

if cos x=12/13, then 12 is the adjacent value and 13 is the hypotenuse value.  to find sin, or opposite/hypotenuse, use the pythagorean identity. opposite=5 and hypotenuse is given as 13. & since it's in quad iv, the sine (or y) value is negative bc it's below the x axis. thus, sin x = -5/13csc is cosecant, or the reciprocal of sine. so csc x = -13/5sec is secant, or the reciprocal of cosine. so sec x = 13/12tan is opp/adj, so tan x = -5/12. it's negative bc tan is negative in quad ivcot is cotangent, or the reciprocal of tangent. so cot x = -12/5

Answer:

  8.  sin x = -5/13

  9.  csc x = -13/5

  10.  sec x = 13/12

  11.  cot x = -12/5

  12.  tan x = -5/12

Step-by-step explanation:

The mnemonic SOH CAH TOA can help you with the sine and tangent. You need to rely on your memory (or notes) to find the reciprocal functions.

The dimensions are such that you can recognize this as a 5-12-13 right triangle. Or, you can use the Pythagorean theorem to find the third side from ... O = -√(H² -A²) = -√(169 -144) = -√25 = -5

The given quadrant tells you that O is negative.

__

8. Sin = Opposite/Hypotenuse

Here, the opposite is -5. The hypotenuse is always taken to be positive.

  sin x = -5/13

__

9. Csc = 1/Sin

  csc x = -13/5

__

10. Sec = 1/Cos

  sec x = 13/12

__

11. Cot = 1/Tan = Adjacent/Opposite

  cot x = 12/-5

  cot x = -12/5

__

12. Tan = Opposite/Adjacent

  tan x = -5/12

Kevin has four apples in a boat each apple weighs 60 G and the empty bowl weighs 40 grams what is the total weight of the four apples with the bow

Answers

9514 1404 393

Answer:

  280 g

Step-by-step explanation:

The total weight is the sum of the weights of the objects:

 total = bowl + apple + apple + apple + apple

We use multiplication to simplify repeated sums:

  total = bowl + 4 × apple

  total = (40 g) + 4 × (60 g) = 40g + 240 g

  total = 280 g

The bowl and 4 apples weighs 280 grams.

A vector has a horizontal component of 14 and a vertical component of 36. Find the direction angle and the magnitude. Direction angle?

Answers

Answer:

The direction angle is 68.73 degrees and its magnitude is 38.62.

Step-by-step explanation:

Given that,

The horizontal component of a vector = 14

The vertical component of a vector = 36

Let the magnitude of a vector is v. So,

[tex]v=\sqrt{14^2+36^2} \\\\=38.62[/tex]

For direction,

[tex]\tena\theta=\dfrac{y}{x}\\\\=\dfrac{36}{14}\\\\\theta=\tan^{-1}(2.57)\\\\=68.73^{\circ}[/tex]

So, the direction angle is 68.73 degrees and its magnitude is 38.62.

What’s the product of (23-8c) - (5c-1)

Answers

Answer:

[tex]40c^{2}[/tex] -123c + 23

Step-by-step explanation:

1. First you need to distribute the negative sign to the second binomial

(23 - 8c) - (5c - 1)

(23 - 8c) (-5c + 1)

2. Distribute each term in the first binomial to each term in the second binomial, FOIL (first, outer, inner, last)

(23 - 8c) (-5c + 1)

-115c + 23 + [tex]40c^{2}[/tex] -8c

3. Combine the like terms

-115c + 23 + [tex]40c^{2}[/tex] -8c

[tex]40c^{2}[/tex] -123c + 23

hope this helps!

What is the slope of this line? Plz

Answers

Answer:

-2

Step-by-step explanation:

Answer:The slope is -2Hope this helps!!

Suzy wants a triangular sandbox. Her dad makes a sandbox/triangle out of boards that are 9 ft, 12 ft, and
15 ft. Does Suzy's sandbox make a right triangle?
O True
O False

Answers

True I just got the answer right

Susan has a piggy bank with 28 coins in it, all dimes and quarters. She has been collecting state quarters and so far has no repeats. If the piggy bank has $5.50. how many more quarters does Susan need before she has a quarter from each of the 50 states?
HELP I WILL GIVE POINTS AND BRAINLIEST​

Answers

Answer:

She needs 32 quarters.

Step-by-step explanation:

d = dime   q = quarters

d + q = 28   so    d = 28-q

0.1d + 0.25q = 5.50

0.10 * (28-q) + 0.25q = 5.50

2.80 - 0.10q + 0.25q = 5.50

0.15q = 5.50 - 2.80

0.15q = 2.70

q = 2.70 / 0.15

q = 18 quarters (she has)

50-18= 32 quarters (she needs)

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