Ok so my Stats professor never explains how to do this stuff

Post Reply New Topic

Below are some questions that I con't understand:
( I have an answer key, but I need to know how you get the answers.)

#1. Find the indicated probability.
A study of consumer smoking habits includes 196 people in the 18-22 age bracket (43 whom smoke), 148 in the 23-30 age bracket (37 whom smoke), and 96 people in the 31-40 age bracket (23 whom smoke). If one person is randomely selected from this sample, find the probability of getting someone who is age 23-30 or smokes?

A. 0.57 B. 0.25 C. 0.486 D. 0.084

#2. 100 employees of a company are asked how they get to work and whether they work full time or part time. The figure below shows the results. If one of the 100 employees is randomely selected, find the probability that the person drives alone or cycles to work.

1. Public transportation: 7 full time, 8 part time 2. Bicycle: 4 full time, 4 part time 3. Drive alone: 30 full time, 29 part time 4. Carpool: 8 full time, 10 part time

A. 0.67 B. 0.34 C. 0.63 D. 0.59

#3. A sample of 4 different calculators is randomely selected from a group containing 41 that are defective and 22 that have no defects. What is the probability that all four of the calculators selected are defective? Round to four decimal places.

A. 0.1794 B. 0.1700 C. 13.8442 D. 0.0829

#4. Find the indicated probability. Round to the nearest thousanth.

A study conducted at a certain college shows that 52% of the school's graduates find a job in their chosen field within a year after graduation. Find the probability that among 8 randomly selected graduates, at least one finds a job in his or her chosen field within a year of graduating?

A. 0.125 B. 0.995 C. 0.520 D. 0.997

#5. A firm uses trend projection and seasonal factors to stimulate sales for a given time period. It assigns "0" if sales fall, "1" if sales are steady, "2" if sales rise moderately and "3" if sales rise a lot. The simulator generates the following output:

0 1 1 2 0 0 1 1 0 0 2 1 0 1 0 2 1 2 0 1 2 0 2 0 3 1 0 2 1 0 1

Estimate the probability that sales will remain steady.

A. 0.125 B. 0.419 C. 0.412 D. 0.355

#6. There are 13 members on a board of directors. If they must form a subcommittee of 6 members, how many different subcommittees are possible?

A. 720 B. 1,235,520 C. 4,826,809 D. 1716

I would greatly appreciate any help from all you math wizzes on here. I am alright at math, but my professor is terrible as he never explains how to do anything and gives homework that has problems completely different from what he talks about in his lessons. If you only know how to do some of them and not all that is alright. Getting an explanation on how to do a few would be really helpful.

I am friends with my stat teacher from highschool on facebook. I wish it wasn't weird to put her name on here.

Alight well that is cool...but how does that help me? Does anyone understand this stuff?

I'm not really a stats guy, but I'll take a shot at some of them.

How many people are 23-30? 148.
How many people smoke? 43 + 37 + 23 = 103.
How many people did we count twice? 37.

So the number we want is 148 + 103 - 37 = 214.

How many total? 196 + 148 + 96 = 440.

So what is the probability? 214 / 440 = 0.4863....

How many people drive alone? 30 + 29 = 59.
How many people cycle? 4 + 4 = 8.

So the number we want is 59 + 8 = 67.

So what is the probability? 67 / 100 = 0.67.

Yes! Thank you! Every little bit helps A LOT! Anyone know how to do any of the others?

How many calculators total? 41 + 22 = 63.
What is the chance that the first calculator is defective? 41 / 63.
What is the chance that the second calculator is defective, given that the first was defective? 40 / 62.
What is the chance that the third calculator is defective, given that the first and second were defective? 39 / 61.
What is the chance that the fourth calculator is defective, given that the first, second and third were defective? 38 / 60.

What is the chance that all of this happens? (41/63) * (40/62) * (39/61) * (38/60) = 0.1700...

First, we will find the probability that none of them find a job.

The chance that any given person doesn't find a job is 0.48.
So the chance that none of the eight find a job is ( 0.48 )^( 8 ) = 0.002817...

So the chance that at least one of them finds a job is 1 - 0.002817... = 0.9971...

The short answer is:
13 choose 6 = (13!) / (6! * 7!) = 1716.

This is a special case of a more general principle.

If you have a set with n elements, and you want to know how many r-element subsets it has, the answer is always
n choose r = (n!) / (r! * (n-r)!)

I have no idea what question 5 is even talking about. Maybe it would only make sense to a statistician.

Hope that helps.

haha! I know seriously! Dude you helped me out so much! If you are in southern California...I should buy you a beer or a sandwich lol.
Would I be able to post some more and you can take a crack at them? You know a lot more than I do...

You can post them, but I might not get around to doing them for a couple days. I bet someone else can take over in the meantime. But the real question is: are you learning how to do them? Getting answers from people is only a short-term strategy, it will cripple you in the long term. I know from experience that it is possible to "help" someone without actually helping them. There must be someone else in your class who is having trouble with the homework. Maybe meet them and talk it over? That's the best way to figure something out, in my experience.

EDIT: This post looks kinda smug and insulting, now that I look at it. But I guess that I really am saying something slightly insulting, and there's no way around it. The point is, I don't really have any way of knowing how much you got out of my answers. Did you just record the answers, or do you see how the methods can be generalised to other questions? Are there any other questions that look similar to the ones you posted? Maybe try doing those ones using the methods I showed you. Or make up your own similar questions with different numbers, and do those. Practice is everything.

Here are a few more:

1. A state lottery involves the random selection of six different numbers between 1 and 27. If you select one six number combination, what is the probability that it will be the winning combination?

A. 1/296,010 B. 1/720 C. 1/387,420,489 D. 1/213,127,200

2. A musician plans to perform 6 selections. In how many ways can she arrange the musical selections?

A. 5040 B. 36 C. 6 D. 720

3. A class has 8 students who are to be assigned seating by lot. What is the probability that the students will be arranged in order from shortest to tallest? (Assume that no two students are the same height.)

A. 1.000 B. 0.0000248 C. 0.00019841 D. 0.00024802

3. The table below shows the soft drinks preferences of people in three age groups

under 21 years of age = 40 for Cola, 25 for root beer and 20 for lemon-lime
between 21 and 40 = 35 for cola, 25 for root beer and 30 for lemon-lime
over 40 years of age = 20 for cola, 30 for root beer and 35 for lemon-lime

If one of the 255 subjects is randomely selected, find the probability that the person is over 40 years of age that they drink root beer.

A. 6/17 B. 5/17 C. 2/5 D. none of the above is correct

Last one:

Evaluate the expression 10P3

A. 27 B. 720 C. 120 D. 7

Well don't worry. I don't think you are insulting me. I have a terrible professor who doesn't actually teach. His lessons are basically him just doing mental masturbation on the board. He almost acts like we are not even there. It is really strange, but that is how I would describe it. Through your explanations so far, I have learned how you got the answers that you did and I would now know how to apply what you taught me on the questions on the upcoming exam. Hopefully you know how to do that last few I posted. Thanks again truly. =)

Okay, I'm a little bit more encouraged.

It's just that I love helping people with maths and thinking about how to explain maths concepts, in fact maths education is one of my "special interests"! So I can easily be "used", and I have been used by people in the past. What I mean is, I was always willing to help them, but sometimes they weren't willing to put in the practice and really learn the techniques for themselves.

Based on what you have helped me out with so far...I can confidently claim that you are a better math teacher then my professor haha. Those last ones I posted are similar to the ones you anwsered before, but he seems to always gives me special case problems...which usually stump me.