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Statistics help please!

Hiya guys
So my teacher gave me homework with this question in it (probability question):

there are 125 college staff.
there are 42 males in academic. 7 in administration and 26 in support.
there are 28 females in academic, 13 in administration and 9 in support.
Given that 90% of academic staff have cars, 80% of admin staff had cars, and 30% if support staff have cars, a staff member is selected at random and found to have a car. What is the probability that this person in a member of the support staff?

I'm stumped. Any help?
Reply 1
Avatar for TeeEm
TeeEm
19
Original post by X3X4fr
Hiya guys
So my teacher gave me homework with this question in it (probability question):

there are 125 college staff.
there are 42 males in academic. 7 in administration and 26 in support.
there are 28 females in academic, 13 in administration and 9 in support.
Given that 90% of academic staff have cars, 80% of admin staff had cars, and 30% if support staff have cars, a staff member is selected at random and found to have a car. What is the probability that this person in a member of the support staff?

I'm stumped. Any help?



best modelling for this is to draw a two way table with the data.

once you have done this and tallied it along and across

look at the total for people with cars ...

and the answer might follow.
Reply 2
Avatar for X3X4fr
X3X4fr
OP
2
I drew a table already, but the thing is that I'm confused with the probability. Do I divide the no. of support staff with cars by total support staff, or multiply the probability of a staff member with a car by the probability of support staff having a car?
Reply 3
Avatar for TeeEm
TeeEm
19
Original post by X3X4fr
I drew a table already, but the thing is that I'm confused with the probability. Do I divide the no. of support staff with cars by total support staff, or multiply the probability of a staff member with a car by the probability of support staff having a car?


I cannot see the table but if it is correct

you are picking out of the total "people with cars" the box which has support members.

it is simply something out of something.
Reply 4
Avatar for X3X4fr
X3X4fr
OP
2
number of Support staff with cars is 10, and total no of people with cars is 89
so will the answer be 10/89?
PS. I don't know how to draw a table in my reply
(edited 9 years ago)
Reply 5
Avatar for TeeEm
TeeEm
19
Original post by X3X4fr
number of Support staff with cars is 10, and total no of people with cars is 89
so will the answer be 10/89?
PS. I don't know how to draw a table in my reply


if your table is correct then this is the answer!
Reply 6
Avatar for TeeEm
TeeEm
19
Original post by X3X4fr

PS. I don't know how to draw a table in my reply


You can also take a picture or scan and attach it (look at menus)

Also you get a quicker response if you use the quote button.
For instance at the moment I am doing my own work and unless I get a notification that someone is responding to my quote I do not know there has been a reply unless I refresh the screen...
Reply 7
Avatar for X3X4fr
X3X4fr
OP
2
Thank you! this was a particularly fishy question for me!
I just have another question. Why shouldn't I find the intersection (i think the two events are independent) of the support staff with cars and total staff with cars?
Reply 8
Avatar for TeeEm
TeeEm
19
Original post by X3X4fr
Thank you! this was a particularly fishy question for me!
I just have another question. Why shouldn't I find the intersection (i think the two events are independent) of the support staff with cars and total staff with cars?



How do you know they are independent?
Reply 9
Avatar for X3X4fr
X3X4fr
OP
2
Original post by TeeEm
How do you know they are independent?

Good point! I just assumed they were :P
Reply 10
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TeeEm
19
Original post by X3X4fr
Good point! I just assumed they were :P


also you used the quote button. Very good!
Reply 11
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X3X4fr
OP
2
Original post by TeeEm
also you used the quote button. Very good!

:smile:

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