Correct answers??

Hey, do you guys think I have these answer right?


Bianca made up a new game to raise money for her dance club. She put 100 tickets into a small drum. Seven tickets had the number two on them, 23 had the number five, 34 had the number eight and there were 36 tickets with the number 11. A person donates the number of cents corresponding to the number on the ticket they draw from the drum. Bianca continues to select players until all tickets are gone.

Let X be the probability distribution of the number of cents donated.

1. The probability distribution for the random variable X is given in the table bellow.



a. Calculate how much Bianca can expect to make for her club using this game.


My answer:
E[X] = 2 x 0.07 + 5 x 0.23 + 8 x 0.34 + 11 x0.36 = 7.96
Not sure if thats $7.96 or I just got it wrong....


b. Calculate the variance of X

Seeing I had to use the above answer to figure this out.... It will be wrong if 1a. is incorrect.

My answer: 71.35


c. Calculate the expected values of the random variable Y = 10X+5

My answer:

E [Y] = 25 x 0.07 + 55 x 0.23 + 85 x 0.34 + 115 x 0.36
= 84.7

But Y = 10X+5

so E[10X+5] = 84.7
Therefore 10E[X]+5 = 7.9+5
= 12.9

d. Calculate the variance of the random variable Y+10X+5

My answer:

E[Y] = 84.7
E[Y^2] = 25^2 x 0.07 + 55^2 x0.23 + 85^2 x 0.34 + 115^2 + 0.36

= 16421.36 (2d.p)

This answer seems way too big..... =/



If you guys could please tell me whats correct and incorrect and maybe help me figure out the questions/answers that I got wrong.

Thanks heaps!

zaimba6 said:

Let X be the probability distribution of the number of cents donated.

1. The probability distribution for the random variable X is given in the table bellow.

X	2	5	8	11
P(X=x)	0.07	0.23	0.34	0.36

a. Calculate how much Bianca can expect to make for her club using this game.

My answer: 7.96
Not sure if thats $7.96 or I just got it wrong.... it doesn't seem like much money at all.

Click to expand...

How did you get that incorrect answer? Hard to help you if we don't no where you are.

Note: This is mathematics, how it "seems" is not of much value. Prove it or don't!

tkhunny said:

How did you get that incorrect answer? Hard to help you if we don't no where you are.

Note: This is mathematics, how it "seems" is not of much value. Prove it or don't!

Click to expand...

Lol people are MEAN on this site

All I'm trying to do is get a lil help....

Ok so my working is bellow

1a.

E[X] = 2 x 0.07 + 5 x 0.23 + 8 x 0.34 + 11 x0.36

= 7.96

I haven't met anyone mean.

Quick Check:

2*0.07 = 0.14
5*0.23 = 1.15
8*0.34 = 2.72
11*0.36 = 3.96

0.14 + 1.15 = 1.29
1.29 + 2.72 = 4.01
4.01 + 3.96 = 7.97

This is why I asked. I don't understand how you managed 7.96. Until we figure out why your calculator isn't working, I'm not sure how we can track this one down with any reliability.

zaimba6 said:

Lol people are MEAN on this site

All I'm trying to do is get a lil help...

Click to expand...

We're not MEAN, just serious. (Oh, maybe overly blunt sometimes, too -- try not to take it seriously.)

We take you seriously. If you ever go to college, I guarantee that they will take you seriously.

Also, this is a tutoring site. (Did you happen to miss the post titled, "Read Before Posting"?) We do not teach classroom material here or lead people around by the hand (i.e., do their thinking for them).

People show us their work or ask specific questions, and we respond based on what we see.

PS: Welcome to both the boards and the real world. :cool:

tkhunny said:

I haven't met anyone mean.

Quick Check:

2*0.07 = 0.14
5*0.23 = 1.15
8*0.34 = 2.72
11*0.36 = 3.96

0.14 + 1.15 = 1.29
1.29 + 2.72 = 4.01
4.01 + 3.96 = 7.97

This is why I asked. I don't understand how you managed 7.96. Until we figure out why your calculator isn't working, I'm not sure how we can track this one down with any reliability.

Click to expand...

I just put the equation in my classpad again, and it still came back with 7.96... but thanks for pointing that out

mmm4444bot said:

We're not MEAN, just serious. (Oh, maybe overly blunt sometimes, too -- try not to take it seriously.)

We take you seriously. If you ever go to college, I guarantee that they will take you seriously.

Also, this is a tutoring site. (Did you happen to miss the post titled, "Read Before Posting"?) We do not teach classroom material here or lead people around by the hand (i.e., do their thinking for them).

People show us their work or ask specific questions, and we respond based on what we see.

PS: Welcome to both the boards and the real world. :cool:

Click to expand...

As you can see, I've done a lot of thinking, I just need to know if I'm going in the right direction with this. I've been unwell since I was 10 (I'm 18 now) so after missing so much school my mum decided I should do my last year at home. The only problem is, they send me out booklets to learn from and then I post them back to be marked. I can't contact them for help ect. The booklets are entirely clear so I just wanted someone to point me in the right direction if I made any mistakes ect. as I figured these questions would be really easy for some people to figure out.

And college?? Sorry I'm from New Zealand, just wondering if this is the same as university?? If so, I won't be attending university as my health prevents me from leaving the house too much at the moment, it's my goal to at least finnish high school.

I'm sure that you will finish high school.

Gosh, you can't ask questions about your course material? Who is the teacher supposed to be? Your mum? You, lol?

We have a similar situation in the USA. Too many machines teaching kids now; inadequate lessons or computer goofs, and nobody to help; kids end up being the teacher, the troubleshooter, and the student. Not good.

I hope that you figure out your gizmo's arithmetic issue, and I wish you good fortune.

Hello, I'm not sure what's wrong with your calculator but I suggest you use a different one.

Now for 1a it's good but should be 7.97.

For 1b you are half way there but you haven't yet figured out the variance, remember Var[X] = E[X^2] - mean^2 so you need to subtract mean^2 from 71.35..

1c is perfect

For 1d again you need a new calculator because the answer to your equation should be 7957 not 16421.36 (2d.p). And again you are only half way there. subtract mean^2 from 7957.










Also don't worry about reason in maths.. maths will try to trick you.


Message me if you are looking for any other help regarding your statistics correspondence, I have just finished doing exactly what you are doing.

Elliot