Help with statistics (uni level) - it's URGENT (2 Viewers)

[ChockoRepublic]

5) Site preparation for new housing developments for tracts of 40 houses is normally distributed with a mean of 200 workdays and a standard deviation of 20 workdays.

a. Find the probability that the site will not be completed within 240 days

b. Find the number of workdays that represent a probability of 0.99 that the site is completed

c. Find the probability that the site is completed between 220 and 240 workdays

d. Find the probability that the site is completed in less than 150 workdays or it takes more than 250 workdays.

7) The probability that a customer would purchase a washing machine is 0.5. The probability that the customer would purchase a washing machine or a dryer is 0.70. The probability that the customer would purchase a dryer is 0.25.

Find out:

(a) the probability that a customer would purchase a washing machine and a dryer

(b) the probability that a customer would purchase a washing machine but not a dryer

(c) the probability that a customer would purchase a dryer, given that the customer purchased a washing machine

(d) the probability that a customer would purchase a dryer, given that the customer did not purchase a washing machine

(e) the probability that a customer would purchase a washing machine, given that the customer purchased a dryer.

Thanks guys. I'm really stuck on these questions.

<3

 

[ChockoRepublic]

anyone?

 

[quik.]

For 5 c. (and any similar ones in next question) you simply refer to the standard deviation distribution curve thing.. I'll see if I can find one but you should know what I mean. Been a while since I did anything related to the others but will edit if my brain starts kicking over.

Edit: this

 

[Fortify]

Isn't this the HSC forum ?

 

[ChockoRepublic]

For 5 c. (and any similar ones in next question) you simply refer to the standard deviation distribution curve thing.. I'll see if I can find one but you should know what I mean. Been a while since I did anything related to the others but will edit if my brain starts kicking over.

Edit: this

thanks man. appreciate it.

Isn't this the HSC forum ?

i thought you little cunts might be able to help as well.

 

[jeff.wong]

7) The probability that a customer would purchase a washing machine is 0.5. The probability that the customer would purchase a washing machine or a dryer is 0.70. The probability that the customer would purchase a dryer is 0.25.

Find out:

(a) the probability that a customer would purchase a washing machine and a dryer
0.05

(b) the probability that a customer would purchase a washing machine but not a dryer
0.45

(c) the probability that a customer would purchase a dryer, given that the customer purchased a washing machine
0.10

(d) the probability that a customer would purchase a dryer, given that the customer did not purchase a washing machine
0.20

(e) the probability that a customer would purchase a washing machine, given that the customer purchased a dryer.
0.20

Not 100% sure - used a venn diagram.

 

[Fortify]

thanks man. appreciate it.



i thought you little cunts might be able to help as well.

Definitely not, esp when it's in the 2U maths section

 

[ChockoRepublic]

7) The probability that a customer would purchase a washing machine is 0.5. The probability that the customer would purchase a washing machine or a dryer is 0.70. The probability that the customer would purchase a dryer is 0.25.

Find out:

(a) the probability that a customer would purchase a washing machine and a dryer
0.05

(b) the probability that a customer would purchase a washing machine but not a dryer
0.45

(c) the probability that a customer would purchase a dryer, given that the customer purchased a washing machine
0.10

(d) the probability that a customer would purchase a dryer, given that the customer did not purchase a washing machine
0.20

(e) the probability that a customer would purchase a washing machine, given that the customer purchased a dryer.
0.20

Not 100% sure - used a venn diagram.

cool, thanks for that. can you have a go at the second one please?

 

[jeff.wong]

5) Site preparation for new housing developments for tracts of 40 houses is normally distributed with a mean of 200 workdays and a standard deviation of 20 workdays.

a. Find the probability that the site will not be completed within 240 days
z = 240-200/20 = 2.00
Look up Z table and it should be .4772 so .5-4.772 = .0228 =2.28%

b. Find the number of workdays that represent a probability of 0.99 that the site is completed
Look up equilavent value for z i.e. what z value gives a probability of .492
z = 2.33

2.33 = (x - 200)/20
Solve for x
x = 246.6

c. Find the probability that the site is completed between 220 and 240 workdays

Do it like a)

z = 220-200/20
z = 240-200/20

Find the area under the probability curve between these 2 z values


d. Find the probability that the site is completed in less than 150 workdays or it takes more than 250 workdays.

do the same as above but this time its outside the to value rather than inbetween like in c.

EDIT: after you find z values you can essentially plug it in online calculators like this and it will auto do for you or you can do it manually using z-tables.

http://25yearsofprogramming.com/javascript/probability.htm

 

[ChockoRepublic]

thanks man. you know for the one that you used a venn diagram to solve, how sure are you of the answers?

 

[jeff.wong]

Pretty sure just double check