3. P343. 13. A sociologist is interested in surveying workers in computer-related jobs to estimate the proportion of such workers who has changed jobs within the past years. (a) In the absence of preliminary data, how large a sample must be taken to ensure that a 95% confidence interval will specify the proportion to within ±0.05? (b) In a sample of 100 workers, 20 of them had changed jobs within the past year. Find a 95% confidence interval for the proportion of workers who have changed jobs within the past year. (c) Based on the data in part (b), estimate the sample size needed so that the 95% confidence interval will specify the proportion to within ±0.05.

Answer:

a) A sample of 385 must be taken.

b) The 95% confidence interval for the proportion of workers who have changed jobs within the past year is (0.1216, 0.2784).

c) A sample of 246 is needed.

Step-by-step explanation:

Question a:

In a sample with a number n of people surveyed with a probability of a success of [tex]\pi[/tex], and a confidence level of [tex]1-\alpha[/tex], we have the following confidence interval of proportions.

[tex]\pi \pm z\sqrt{\frac{\pi(1-\pi)}{n}}[/tex]

In which

z is the zscore that has a pvalue of [tex]1 - \frac{\alpha}{2}[/tex].

The margin of error is:

[tex]M = z\sqrt{\frac{\pi(1-\pi)}{n}}[/tex]

Absence of preliminary data:

This means that we use [tex]\pi = 0.5[/tex], which is when the largest sample will be needed.

95% confidence level

So [tex]\alpha = 0.05[/tex], z is the value of Z that has a pvalue of [tex]1 - \frac{0.05}{2} = 0.975[/tex], so [tex]Z = 1.96[/tex].

How large a sample must be taken to ensure that a 95% confidence interval will specify the proportion to within ±0.05?

A sample of n must be taken.

n is found when [tex]M = 0.05[/tex]. So

[tex]M = z\sqrt{\frac{\pi(1-\pi)}{n}}[/tex]

[tex]0.05 = 1.96\sqrt{\frac{0.5*0.5}{n}}[/tex]

[tex]0.05\sqrt{n} = 1.96*0.5[/tex]

Dividing both sides by 0.05

[tex]\sqrt{n} = 1.96*10[/tex]

[tex](\sqrt{n})^2 = (19.6)^2[/tex]

[tex]n = 384.16[/tex]

Rounding up,

A sample of 385 must be taken.

Question b:

In a sample of 100 workers, 20 of them had changed jobs within the past year.

This means that [tex]n = 100, \pi = \frac{20}{100} = 0.2[/tex]

The lower limit of this interval is:

[tex]\pi - z\sqrt{\frac{\pi(1-\pi)}{n}} = 0.2 - 1.96\sqrt{\frac{0.2*0.8}{100}} = 0.1216[/tex]

The upper limit of this interval is:

[tex]\pi + z\sqrt{\frac{\pi(1-\pi)}{n}} = 0.2 + 1.96\sqrt{\frac{0.2*0.8}{100}} = 0.2784[/tex]

The 95% confidence interval for the proportion of workers who have changed jobs within the past year is (0.1216, 0.2784).

Question c:

Same procedure as question a, just with [tex]\pi = 0.2[/tex]

[tex]M = z\sqrt{\frac{\pi(1-\pi)}{n}}[/tex]

[tex]0.05 = 1.96\sqrt{\frac{0.2*0.8}{n}}[/tex]

[tex]0.05\sqrt{n} = 1.96\sqrt{0.2*0.8}[/tex]

[tex]\sqrt{n} = \frac{1.96\sqrt{0.2*0.8}}{0.05}[/tex]

[tex](\sqrt{n})^2 = (\frac{1.96\sqrt{0.2*0.8}}{0.05})^2[/tex]

[tex]n = 245.8[/tex]

Rounding up

A sample of 246 is needed.

I need some help! I would really appreciate it!

Ms. Vasquez's daughter lives 1,650 miles away. Ms. Vasquez won a gift card for 100 gallons of gas. If her car can travel 35 miles on each gallon, can she travel roundtrip to see her daughter on free gas? Explain how you know.

What is the range for the set of data?

A. 4
B. 6
C. 3.5
D. 0


I don’t want a link, so if you were gonna send one, ignore this instead

17.
Which pair of numbers is relatively prime? *


7 & 21
4 & 15
ОООО
6 & 9
9 & 27

what is 2 x 2? answer dumly

CAn someone help me plsss

Helpppppppppppppooopp

I have no clue how to do this! please help me!!!

what is the domainof f(x)=4^x

Select all numbers that have and absolute value of 0.6

3.65 is greater than or less than 3and1/5​

Can you please help me do a and b I will reward brainliest

Anna charges $8.50 an hour to babysit how long will it take to make $51.00

5/8 - 1/4 simplest form​

What is a good estimate for this angle measurement? A. 10 degrees B. 25 degrees C. 75 degrees D. 95 degrees

Kristy is going to a college where tuition is $8,000 per year. She has a scholarship that pays 80% of tuition. Her aunt is giving her $1,000 per year. How much will Kristy need to borrow to pay tuition each year?​

A hexagonal prism has a base with an area of 15 square inches and the volume is 105 cubic inches.
.
Complete the sentence about the height of the prism.

The height of the prism is _____ inches,square inches,cubic inches

Hi I need to send you a screenshot .​

Unit 10: Circles ** please show how you got the answer ** i know the answer is 108° but i don’t know how to get it.

can anyone solve these and show work? please help a girl out lol

please answer i will give crown :D

Solve for x.
109= -x + 267
X=
x 5
?

Omlll, I'm actually stuck rn xD If anyone can help,i'd appreciate it so much!! Tyssmm!!!!!

Select ALL TRUE statements about Linear Functions:
Group of answer choices

The degree of the function is one.

The y values change by a common difference.

The graph is a straight line.

Vertex form is used for graphing.

800:2 in the simplest form

A manufacturer of potato chips would like to know whether its bag filling machine works correctly at the 434 gram setting. It is believed that the machine is underfilling the bags. A 9 bag sample had a mean of 431 grams with a variance of 144. A level of significance of 0.01 will be used. Assume the population distribution is approximately normal. Is there sufficient evidence to support the claim that the bags are underfilled

Just want to confirm the answer is 4 more student because from 6 to 10 is 4
More or I’m wrong ?? Just please help me with yes or no thanks

Help please will mark brainliest

Help please !! need it adap

A tutor earns $220 for 4 hours of tutoring. At the same rate, how much would the tutor earn for 3 hours of tutoring?

A. $150
B. $155
C. $165
D. $180