Math Is Fun Forum

qfreddy95

Member

Registered: 2011-05-05

Posts: 8

PAID math 150 statistics

Hello, my name is Freddy.
I have a few math 150 statistics questions for an expert. there are 11 questions.

[personal information removed by moderator]

thanks.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: PAID math 150 statistics

Hi qfreddy95;

You broke every rule possible. First of all, post your questions, everyone here is a volunteer. I or someone else will do them if we can. For free I might add.

Also for your own security, never post your email address like that.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

qfreddy95

Member

Registered: 2011-05-05

Posts: 8

Re: PAID math 150 statistics

Thanks for reply Bobbym and apologies for breaking the rules. I didn't want to post them all like this because it takes too much space. Appreciate any input.

1. Among companies doing bridge construction, 80% test employees for substance abuse. A study involves the random selection of 10 such companies. Find the probability that exactly 5of the 10 companies test for substance abuse (assume binomial distribution)

2. Among companies doing bridge construction, 80% test employees for substance abuse (see above). For the group of 10 companies, find the mean and standard deviation for the number (among 10) that test for substance abuse.

3. a) A set of data items is normally distributed with a mean of 60. Convert the data item x=56 to a z-score, if the standard deviation is 4.
   b) A set of data items is normally distributed with a mean of 500 and a standard deviation of 70. Find the data item in this distribution that corresponds to the z-score z= - 1.5

4. The tire corporation claims that the useful life of its tire is normally distributed with a mean life of 28,000 miles and a standard deviation of 4000 miles. What percentage of the tiers are expected to last more than 35,000 miles?

5. The number of major earthquakes is a year is approximately normally distributed with a mean of 20.8 and a standard deviation of 4.5. Find the probability that in a given year there will be between 18 and 23 earthquakes.

6. Birth weights in the united states are normally distributed with a mean of 3420 g and a standard deviation of 495 g. If a hospital plans to set up special observation conditions for the lightest 2% of babies, what weight is used for the cut - off seperatng the lighest 2% from others.

7. Using the Central Limit Theorem that women's heights are normally distributed with a mean of 63.6 in. and a standard deviation of 2.5 in.

a) If a 1 woman is randomly selected, find the probaility that the height is less than 64 in.

b) If 36 women are randomly selected, find the probability that they have a mean height less than 64 in.

8. Find the critical value Za/2 that corresponds to a 98% confidence level.

9. Use sample data and confidence level to construct the confidence interval estimate of the population proportion p: n = 2000, x = 400, 95% confidence.

10. Use the margin of error E= 0.5 in, confidence level 95% and population standard deviation Q = 2.5 in to find the minimum sample size required to estimate an unknown population mean.

11. (Show the work).
A professor has found that the grades on the statistical final are normally distributed with a mean of 72 and a standard deviation of 12.5. The top 8% of the class will receive an A; the next 20%, a B; the next 42%, a C; the next 18%, a D; and the bottom 12%, an F.
What avarage must you obtain to pass the course? (You'll need a D or better)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: PAID math 150 statistics

Hi;

No problem:

1)

2) The mean is 8. The standard deviation is:

Using the formula for sd:

3)

a) That is -1 standard deviations from the mean.

b) 395 is -1.5 standard deviations from the mean.

4) 4% of their tires are expected to last more than 35000 miles.

5) 42% chance.

6) 98% of the babies will weigh more than 2404 gms. So I guess that is the cutoff point.

7) The central limit theorem states that when drawing a random sample from a distribution, it will be approximately normally distributed if it is large enough.

a) Probability is .4364

b) I am not sure here but I think the sd of the sample is

Using a z chart.

8) 2.33

9) I do not remember how to find these.

10) Pretty tentative here. I am getting an answer of 96, notes say 97?!

Notes say to round up, so 96.04 -> 97

11) A 57.35 score is necessary to pass. Presumably the teacher will round up to 58 is needed to pass.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

qfreddy95

Member

Registered: 2011-05-05

Posts: 8

Re: PAID math 150 statistics

Bobbym, thanks it's already a HUGE help. don't want to look rude, is there a possibility to explain the steps you take to solve the problems.
thanks a lot.

Last edited by qfreddy95 (2011-05-05 17:48:40)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: PAID math 150 statistics

Hi;

I will flesh them out as much as I can after I have finished solving them.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

gAr

Member

Registered: 2011-01-09

Posts: 3,482

Re: PAID math 150 statistics

Hi,

11)
I used a table here: http://www.statsoft.com/textbook/distribution-tables/

---

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: PAID math 150 statistics

Hi gAr;

Sorry, I just added that to mine. I did not see your post.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

gAr

Member

Registered: 2011-01-09

Posts: 3,482

Re: PAID math 150 statistics

Hi bobbym,

No problem!

---

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

qfreddy95

Member

Registered: 2011-05-05

Posts: 8

Re: PAID math 150 statistics

hi Bobbym and gAr, thanks for the response, appreciate it.

Bobbym how may I contact you to make money transfer?

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: PAID math 150 statistics

Hi qfreddy95;

I am a billionaire, or at least the rest of my family are. The next time you see someone on the street who needs it, give it to him or her. Or do something for someone else that you would not ordinarily do. I am expecting you to do that.

Anyway, this is overdue, Welcome to the forum!

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

qfreddy95

Member

Registered: 2011-05-05

Posts: 8

Re: PAID math 150 statistics

Hi there Bobbym and thanks for the welcome!
Your funds are being sent towards American National Red Cross for Japan relief.
Thanks again.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: PAID math 150 statistics

Hi;

Your welcome.

Good choice, and good luck.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

qfreddy95

Member

Registered: 2011-05-05

Posts: 8

Re: PAID math 150 statistics

Hi guys, I have some more questions, could anyone help with these? thanks in advance.

1.The test statistic in a left tailed test is z = -1.25

2. The test statistic in a left tailed test is z = 1.75

3. With H1: p = (equal sign crossed) 0.707, the test statistic is z = - 2.75

4. With H1: p < 0.777, the test statistic is z = - 2.95

5. Random guesses are made for 50 SAT multiple choice questions, so n = 50 and p = 0.2

6. 300 subjects are tested and the probability of a positive result is 0.48, so n = 300 and p = 0.48

7. The midterm exam in nursing course consists of 75 true/false questions. Assume that unprepared student makes random guesses for each of the questions.

8. In the US 40% of the population have brown eyes. If 14 people are randomly selected, find the probability that at least 12 of them have brown eyes. Is it unusual to select 14 people and randomly select 12 that have brown eyes?

9. Ten peas are generated from parents having the green/yellow pair of genes, so there is 0.75 probability that an individual pea will have a green pod. Find the probability that among the 10 offspring peas, at least 9 have green pods. Is it unusual or not.

10.  finding probability:
Z0.05 ?

P (-1.96 < z < 1.96) ?

P (z < - 2.575 or z > 2.575) ?

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: PAID math 150 statistics

5. Random guesses are made for 50 SAT multiple choice questions, so n = 50 and p = 0.2

How many choices are available for each question? It appears that it is a 5 multiple choice question.

6. 300 subjects are tested and the probability of a positive result is 0.48, so n = 300 and p = 0.48

Yes.

7) n = 75 and p = .5

8. In the US 40% of the population have brown eyes. If 14 people are randomly selected, find the probability that at least 12 of them have brown eyes. Is it unusual to select 14 people and randomly select 12 that have brown eyes?

The question is awful. Since you can not pick the same person twice it is actually a hypergeometric distribution. But since the total population is left out I am forced to use the binomial distribution.

It is very unusual.

9)

It is not unusual.

10.  finding probability:
Z0.05 ?

P (-1.96 < z < 1.96) ?

P (z < - 2.575 or z > 2.575) ?

What does Z0.05 ? mean?

P (-1.96 < z < 1.96) = .95

P (z < - 2.575 or z > 2.575) = .99

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

qfreddy95

Member

Registered: 2011-05-05

Posts: 8

Re: PAID math 150 statistics

Bobbym thanks for the replies. I cant say enough how thankful I'm for your help.

i'd like to ask you what do you think about the first 4 questions?

Finding p-values. Also use a 0.05 significance level and state the conclusion about the null hypothesis (reject the null hypothesis or fail to reject the null hypothesis)

1.The test statistic in a left tailed test is z = -1.25

2. The test statistic in a left tailed test is z = 1.75

3. With H1: p ≠ 0.707, the test statistic is z = - 2.75

4. With H1: p < 0.777, the test statistic is z = - 2.95

Last edited by qfreddy95 (2011-05-10 17:29:43)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: PAID math 150 statistics

Hi;

I left these out because I am not sure on them.

1) z value is not less than -1.65 so you cannot reject the null hypothesis.

2) Same as above.

The other two I am looking at.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

qfreddy95

Member

Registered: 2011-05-05

Posts: 8

Re: PAID math 150 statistics

thanks Bobbym.

van364

Member

Registered: 2011-11-06

Posts: 13

Re: PAID math 150 statistics

I'm having trouble with this one whould you please explain to me how to do this?

7. The midterm exam in nursing course consists of 75 true/false questions. Assume that unprepared student makes random guesses for each of the questions.
Would it be unusual for a student to pass the exam by guessing and getting at least 45 correct answers? Why or why not?

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: PAID math 150 statistics

Hi;

Depends on what you have already established as unusual.

The probability of getting 45 to 75 on a multiple choice test like that is:

Done by the binomial distribution. That is slightly more than a 5% chance of that happening by luck.

There is another way to arrive at this answer.

So 4.33 is 1 standard deviation.
The mean is 37.5. Know how to figure it from here?

Welcome to the forum.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.