In a sample of 100 steel wires the average breaking strength is 50 kN, with a standard deviation of 2 kN. a. Find a 95% confidence interval for the mean breaking strength of this type of wire. b. Find a 99% confidence interval for the mean breaking strength of this type of wire. c. An engineer claims that the mean breaking strength is between 49.7 kN and 50.3 kN. With what level of confidence can this statement be made? d. How many wires must be sampled so that a 95% confidence interval specifies the mean breaking strength to within ±0.3 kN? e. How many wires must be sampled so that a 99% confidence interval specifies the mean breaking strength to within ±0.3 kN?

Answer:

.

Step-by-step explanation:

1.

Alpha = 0.05. alpha/2 = 0.025

Under the z table

Z 0.025 = 1.96

50+-1.96(2/√100)

= 50+-0.39

50+0.39 = 50.39

50-0.39 = 49.61

2.

At 99%

Alpha = 0.01

Alpha/2 = 0.005

In z table

= 2.58

50+-(2.58)(2√100)

= 50 +- 0.52

= 50+0.52 = 50.52

50 - 52 = 49.48

Please check attachment for answers 3 to 5. The test editor did not work properly. It kept flagging some of my typed content.

Using the z-distribution, it is found that:

a) The 95% confidence interval for the mean breaking strength of this type of wire, in kN, is (49.61, 50.39).

b) The 99% confidence interval for the mean breaking strength of this type of wire, in kN, is (49.49, 50.52).

c) The confidence level is of 86.64%.

d) 171 wires must be sampled.

e) 295 wires must be sampled.

We are given the standard deviation for the population, which is why the z-distribution is used to solve this question.

The information given is:

The confidence interval is:

[tex]\overline{x} \pm z\frac{\sigma}{\sqrt{n}}[/tex]

The margin of error is of:

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

Item a:

The first step is finding the critical value, which is z with a p-value of [tex]\frac{1 + \alpha}{2}[/tex], in which [tex]\alpha[/tex] is the confidence level.

In this problem, [tex]\alpha = 0.95[/tex], thus, z with a p-value of [tex]\frac{1 + 0.95}{2} = 0.975[/tex], which means that it is z = 1.96.

Hence, the interval is:

[tex]\overline{x} - z\frac{\sigma}{\sqrt{n}} = 50 - 1.96\frac{2}{\sqrt{100}} = 49.61[/tex]

[tex]\overline{x} + z\frac{\sigma}{\sqrt{n}} = 50 + 1.96\frac{2}{\sqrt{100}} = 50.39[/tex]

The 95% confidence interval for the mean breaking strength of this type of wire, in kN, is (49.61, 50.39).

Item b:

[tex]\alpha = 0.99[/tex], thus, z with a p-value of [tex]\frac{1 + 0.99}{2} = 0.995[/tex], which means that it is z = 2.575.

[tex]\overline{x} - z\frac{\sigma}{\sqrt{n}} = 50 - 2.575\frac{2}{\sqrt{100}} = 49.49[/tex]

[tex]\overline{x} + z\frac{\sigma}{\sqrt{n}} = 50 + 2.575\frac{2}{\sqrt{100}} = 50.52[/tex]

The 99% confidence interval for the mean breaking strength of this type of wire, in kN, is (49.49, 50.52).

Item c:

The margin of error is:

[tex]M = \frac{50.3 - 49.7}{2} = 0.3[/tex]

Hence:

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

[tex]0.3 = z\frac{2}{\sqrt{100}}[/tex]

[tex]0.2z = 0.3[/tex]

[tex]z = 1.5[/tex]

z = 1.5 has a p-value of 0.9332, hence:

[tex]\frac{1 + \alpha}{2} = 0.9332[/tex]

[tex]1 + \alpha = 2(0.9332)[/tex]

[tex]\alpha = 0.8664[/tex]

The confidence level is of 86.64%.

Item d:

This is n for which M = 0.3, with z = 1.96, hence:

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

[tex]0.3 = 1.96\frac{2}{\sqrt{n}}[/tex]

[tex]0.3\sqrt{n} = 1.96(2)[/tex]

[tex]\sqrt{n} = \frac{1.96(2)}{0.3}[/tex]

[tex](\sqrt{n})^2 = \left(\frac{1.96(2)}{0.3}\right)^2[/tex]

[tex]n = 170.7[/tex]

Rounding up, 171 wires must be sampled.

Item e:

Now z = 2.575, hence:

[tex](\sqrt{n})^2 = \left(\frac{2.575(2)}{0.3}\right)^2[/tex]

[tex]n = 294.7[/tex]

Rounding up, 295 wires must be sampled.

A similar problem is given at https://brainly.com/question/25325640

How many pounds are there in 2 3/4 tons? (1 ton = 2000 pounds)

Which loan or loans listed below are awarded based on the financial need of the student?

I. Perkins loan
II. subsidized Stafford loan
III. unsubsidized Stafford loan
a.
I only
b.
I and II
c.
II and III
d.
I, II, and III

Caroline surveyed 380 of the students in her school about their favorite color. 209 students said their favorite color was blue. What percentage of the surveyed students said their favorite color was blue?

Write an expression to b+b+b+b+b that is that a sum of two terms

whats a better way to solve a polygon and what are the steps to it.

Solve the inequality 4(k − 5) + 12k ≥ −4

help me please I'm in a rush

Which rule describes the function in the graph below?
10
9
8
7
(4.6)
10,6
5
4
3
(-2,2
2
1
3
4 5
B 7
8 9
-7 -6 -5 -4 -3 -2 -14
Ni-
X, XS-2
Save and Exit
Next
Submit
Mark this and retum

2 1/2 =1 2/3 ÷y


i need help please

The height of a parallelogram is 5 feet The base is 7 feet the length is 9 1/2 feet what is the area of the parallelogram

PLEASE ANSWER ASAP!!!!

Rewrite each of the following expressions without using absolute value

-|-3|

help model -5+(-6) on the number line

Maura added 5/8 of a cup of walnuts to a batch of trail mix. Later, she added 3/4 of a cup of almonds. How many cups of nuts did Maura put in the trail mix in all? Write your answer as a fraction or as a whole or mixed number. cups

what is the absolute value of 1

The Hornes buy a trampoline with a regular price of $495.00. It is on sale for 20% off the regular price. After calculating the sale price, they use a coupon for $35.00 off. The salesperson then adds a sales tax of 7%. What is the final price of the trampoline?

Wal-Mart buys paper plates for $3.25 and marks them up for 142%. How much do I buy them for?​

A machine that drills holes for wells drilled to a depth of
–72 feet in one day (24 hours).
If the machine drilled at a constant rate, what was the
depth after 15 hours?

Solve for x.
4x - 36
3x + 10

Assuming that the heights of college women are normally distributed with mean 63 inches and standard deviation 3 inches, what percentage of women are taller than 60 inches?

Please help. Systems of equations. Solve using elimination.
12X + 16y = 96
12X + 48y = 192

If the same number is subtracted from both the numerator and the denominator of 13/17 , the result is 3/5 . Find the number.

seven subtracted from twice a number given 17, find this number.

C, G, and D are collinear. E, G, and F are also collinear. The two lines
intersect at point G. Line EF bisects line CD. Find EG: if CG=5x-1, GD=7x-
13, EF=6x-4, and GF=13.

What’s the Awnser cause I really don’t know

What is the value of x? enter you answer in the box bellow.

2.4 Assignment 4
Alex has a job transporting furniture by truck. His truck is filled with tables that weigh 250 pounds each
and chairs that weigh 20 pounds each. There is a combined total of 300 tables and chairs in his truck.
Let x be the number of tables in his truck. Write an expression for the combined total weight (in
pounds) of the tables and chairs in his truck.
Choose one. 4 points
Total weight in pounds = 230.3 + 50
O
Total weight in pounds = -230.2 + 550
O
Total weight in pounds = -2302 + 75,000
O
Total weight in pounds = 2302 + 6000
Total weight in pounds = 230x + 75,000
Total weight in pounds = -230x + 50
O O
Total weight in pounds = -230x + 6000

What is the cf of 32 and 24?​

Simplify the expression.
(3x\y)^-3

Mayela bought 3.4 pounds of almonds for 21.58. Approximately how many pounds of walnuts can mayela purchase for 1 dollar

Compute using long division: 342 ÷ 23​