Question

@mathmale HALP

Answer 1

#3

Answer 2

Got to hand it to you: You're spunky, fast, determined, motivated.

Answer 3

freshman/ healthy foods.

Answer 4

hehehehe thanks

Answer 5

Can you explain in words what P(A|B) means? What P(B|A) means?

Answer 6

the probability of A given B

Answer 7

right?

Answer 8

Yes. Another way to explain it: Given that Event B has occurred, what is the probability that A will occur?

Answer 9

so, assuming you have created an actual table with numbers in it, with totals of rows and totals of columns, we now focus on any 1 row and any 1 column (your choice of each).

Answer 10

How are your rows labeled? your columns?

Answer 11

P(healthy foods|freshman)
and
P(freshman\healthy foods)

right?

Answer 12

(thinking)

Answer 13

Given that a student selected at random from among your 20 (or more) subjects is a freshman, what is the probability that he or she selects healthy foods? How would you calc. that?

Answer 14

is what i wrote correct?

Answer 15

First, you'd need to know, from your table, how many of your subjects are freshmen.

Answer 16

What you have written is correct as far as it stands. I assume you also have rows for sophs and jrs. but really, for what you are doing RIGHT now, heck with the sophs and jrs.

Answer 17

So, how many of your sweet subjects are frosh?

Answer 18

no i did not include them. making this as painless as possible.

Answer 19

241 of them

Answer 20

uh-oh.
But anyway.
how many frosh?

Answer 21

241

Answer 22

Wow, what a big study. Req'd to use at least 20 subjects, but reb rebels and uses 241 for frosh alone. Wow.

Answer 23

over achiever c;

Answer 24

And, of those 241, how many eat primarily healthy foods?

Answer 25

191 of them

Answer 26

So your conditional prob, the prob that GIVEN that your selected student is a frosh, he or she eats primarily healthy foods, is P(A|B). How would you calculate this, using the 191 and 241 data ?

Answer 27

191/214

Answer 28

Perfect. Just perfect.

Answer 29

WAIT

Answer 30

But now we have to reverse the order: We need to calc P(B|A). In other woerds,

Answer 31

NO

Answer 32

ITS 50/241

Answer 33

given that the sweetie student you've picked eats healthy foods primarily, what is the P that that sweetie is a frosh?

Answer 34

0.20746887966

Answer 35

Without a completely filled in table, how can you answer that?

Answer 36

Hold, hold. Where are we? NO what?

Answer 37

You said there were 241 frosh, and that 191 of them claimed to eat only healthy foods.
P(healthy food | frosh) = 191/241.

Answer 38

no 50 of them i was looking at the ones that eat unhealthy

so its 50/214

Answer 39

214/50 = p(freshy | healthy foods)

Answer 40

It's not 214/50. No probability can be smaller than 0 nor greater than 1.

Try again on that one.

Answer 41

P(B|A) im confused on what i would be plugging in

because P(A|B) is 50/241

Answer 42

First, are you sat. with our previous result, 191/241?

Answer 43

http://prntscr.com/b1jzpg

Answer 44

that is for unhealthy foods

Answer 45

I'm sorry, R, but I'm losing track of where we are and what you want to know.
Please provide some more structure here.

Answer 46

we are doing question #3

here is the chart that i have made http://prntscr.com/b1jzpg
I chose row healthy foods and column freshman

so far i have P(A|B)=50/241 now i have to find P(B|A)

Answer 47

Our communication seems to have broken down over the issue

"214/50 = p(freshy | healthy foods)"

No probability can be less than 0 or greater than 1; 214/50 is 4.28.

Answer 48

All right. How many students, total, eat healthy foods?

Answer 49

111

Answer 50

yes, I have the table in fron t of me, but I'd like to hear it from you. OK, 111 students, total. Now, how many of those 111 students are freshmen?

Answer 51

50

Answer 52

Right. So the condit. prob. is 50/111.

Answer 53

so thats P(B|A)?

Answer 54

Let me put it this way: It's the probability P(student is a freshman | student eats healthy foods).

Answer 55

Given that the student chosen at random eats healthy foods, what is the prob. tht that same student is a frosh? Answer: 50/111.

Answer 56

As explained in a PM some time ago, I'd like to get off the 'Net very, very soon. Is it possible that we could meet again on O. S. tomorrow to finish this discussion?

Answer 57

no can do. its due today. *CRIES*

Answer 58

but ill let you go, thanks for the help.

Answer 59

can you do #4?

Answer 60

yes im fine with #4 just #3 is being a pain

Answer 61

We went over that briefly some time ago.
There are a total of 400 something students.
How many of these students satisfy 2 criteria at once: frosh and healthy (or whatever)?

Answer 62

Weren't we fionished with #3?

Answer 63

If not, what specifically do you still need help with in #3?

Answer 64

If you choose A=frosh and B=healthy foods, we MUST stick with those definitions throughout Problem #3.

Answer 65

can you tell me in words what P(A|B) and P(B|A) is

we have got P(A|B)=50/241

and P(B|A)=50/111 but im lost

Answer 66

Pls verify the meaning of A and B first.
A= the event that ....
B= the event that ... "

Answer 67

hmm. no clue.

Answer 68

If the orig. problem statement doesn't specify that (and I don't think it did), then it's entirely up to you to define A and B according to the situation you designed (healthy foods)

Answer 69

a is healthy goods and b is total for freshman

Answer 70

I'd rather that B: student chosen at random happens to be a freshman, and
A: student chosen at random happens to eat healthy foods

Answer 71

What is P(A|B)? This says we already know that the randomly chosen student is a frosh. Fine. how many frosh have we, total?

Answer 72

okay but how are P(A|B) and P(B|A) different?

Answer 73

why do we plug in different events for both.

Answer 74

gott a finish P(a|B) first.

Pls hold that question; i'm not avoiding it, just want to finish one thing at a time.

Answer 75

yes sir. okay so we have 214 total fresh

Answer 76

P(student eats healthy | student is a frosh) = ?

how many of the 486 students are frosh? 214.
Of those 214, how many eat healthy?

Answer 77

241 sorry. 50 of them each healthy

Answer 78

Nothing to be sorry about. 241 students total, of whom 50 eat healthy.

P(A|B)=50/241. Done.

P(B|A)=? same as P(student is a frosh | student eats healthy)

Answer 79

How many students of both class levels eat healthy?

Answer 80

111

Answer 81

Of those 111 students, how many are frosh?

Answer 82

50

Answer 83

then P(B|A) = 50/111.

Answer 84

Notice that this is NOT the same as P(A|B). We were exploring, hopefully without any predefined conclusion that the two probabilities were the same.

Answer 85

so thats all it was? WHYYY DO I OVER COMPLICATE EVERYTHING?

Answer 86

ugh. thank you for all your patience with me being so slow.

Answer 87

Prob (especially) and stat were originally very, very hard for me.

You're not slow!

Glad to have gotten to know you better and to have achieved some productive results on your questions! Good night.

Answer 88

good night c: and thanks again