• Support PF! Buy your school textbooks, materials and every day products Here!

Probability/Statistics Question

  • Thread starter srfriggen
  • Start date
  • #1
288
3
My brother in law asked me to look at this homework problem for him for a statistics class. He assumes that since I'm taking calculus that I must be able to learn statistics and probability. So I've tried to learn what I can this morning but don't see it going too far.



1. Homework Statement


Suppose that P(A) = .61, P(B) = .42, and P(A [tex]\cap[/tex] B) = .14

Calculate the following:

a) P(A [tex]\cup[/tex] B)

b.) P(A l B)

c.) P(B l A)

d.) P([tex]\bar{A}[/tex] [tex]\cup[/tex] B)

e.) P(A l [tex]\overline{B}[/tex])

f.) P([tex]\bar{A}[/tex] l B)


g) Are A and B independent events? Why or Why not?

h) Are A and B mutually exclusive events? Why or why not?



Homework Equations





The Attempt at a Solution



a) P (A U B) = P(A) + P(B) = .61 + .42 = 1.03. (I feel this is incorrect).

b) I don't know how to calculate or attempt (AlB)

d) I don't know what the line over the A means.

g) The are independent if P(A U B) = P(A)P(B), but .14 not equal to .61 * .42, so not independent.

h) ?



Homework Statement





Homework Equations





The Attempt at a Solution


Homework Statement





Homework Equations





3. The Attempt at a Solution

Homework Statement





Homework Equations





The Attempt at a Solution


Homework Statement





Homework Equations





The Attempt at a Solution


Homework Statement





Homework Equations





The Attempt at a Solution


Homework Statement





Homework Equations





The Attempt at a Solution


Homework Statement





Homework Equations





The Attempt at a Solution

 

Answers and Replies

  • #2
tiny-tim
Science Advisor
Homework Helper
25,832
249
Hi srfriggen! :smile:

Use Venn diagrams to find what to add, and what to subtract.

I guess the bar means "not".

A and B are independent if P(A and B) = P(A)P(B). :wink:
 
  • #3
288
3
so they are not dependent since P(A and B) does not equal P(A)P(B)?

How do I know if they are mutually exclusive?

Is the answer to a) .89? P(A)+P(B) - P(A and B)?

And how do I calculate P(A l B)?



This seems like an easy problem, IF, I was taking probability or statistics haha. but I just don't have the time to learn it today. I have a calc II test wednesday that is taking up all my time.
 
  • #4
tiny-tim
Science Advisor
Homework Helper
25,832
249
so they are not dependent since P(A and B) does not equal P(A)P(B)?
yes
Is the answer to a) .89? P(A)+P(B) - P(A and B)?
yes
How do I know if they are mutually exclusive?

And how do I calculate P(A l B)?
Your brother-in-law should know the definitions of P(A l B), and of "mutually exclusive". :wink:
 
  • #5
288
3
Ok, I think I figured out a few more. Can you let me know if I am correct?...

P(A l B) = P(A or B)/P(B) = .14/.42 = .333

P(B l A) = P(A or B)/P(A) = .14/.61=.229

- Are A and B independent events? Why or why not?
No, b/c P(A or B) does not equal P(A)P(B)

-Are A and B mutually exclusive events? Why or why not?
No, b/c P(A or B) does not equal Zero.


I'll let him figure out the other 3 but I wanna make sure I'm sending him the correct answers or I'll never hear the end of it! lol
 
  • #6
tiny-tim
Science Advisor
Homework Helper
25,832
249
P(A l B) = P(A or B)/P(B) = .14/.42 = .333

P(B l A) = P(A or B)/P(A) = .14/.61=.229

- Are A and B independent events? Why or why not?
No, b/c P(A or B) does not equal P(A)P(B)

-Are A and B mutually exclusive events? Why or why not?
No, b/c P(A or B) does not equal Zero.
Yes, that's all correct, except that every time you've written "or", it should be "and". :wink:
 
  • #7
288
3
haha, I keep getting those symbols confused!

Thanks for your help!
 

Related Threads for: Probability/Statistics Question

  • Last Post
Replies
19
Views
4K
Replies
2
Views
6K
  • Last Post
Replies
6
Views
881
Replies
5
Views
2K
Replies
9
Views
976
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
2
Views
2K
Top