mean, variance, standard dev, expectation of distribution

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MRS.FREE

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can someone please just look over this and make sure im on the right track. thank you! (i didn;t know how to put the squared symbol in so i just typed "sq"...sorry)

2)
x 19 20 21 22 23
p(x) .2 .2 .3 .2 .1

mean=(1.9)(.2)+(20)(.2)+(21)(.3)+(22)(.2)+(23)(.1)=20.8
variance=(19sq)(.2)+(20sq)(.2)+21sq)(.3)+(22sq)(.2)+(23sq)(.1)=434.2 - (20.8)sq=1.6
sd=the sq root of 1.6=1.3

*HOW MANY SHIRTS THE MANAGER PURCHASE IF HE WANTS TO MAKE SURE HE HAS ENOUGH SHIRTS FOR THE NEXT 5 DAYS?
i don't understand how to answer this....PLEASE HELP WITH THIS PART! :)

4)
x 5 6 7 8 9 10
p(x) .05 .2 .4 .1 .15 .1

mean=(5)(.05)+(6)(.2)+(7)(.4)+(8)(.1)+(9)(.15)+10)(.1)=7.4
variance=(5sq)(.05)+(6sq)(.2)+(7sq)(.4)+(8sq)(.1)+(9)(.15)+(10)(.1)=56.6 - (7.4)sq=1.8
sd=the sq root of 1.8=1.3

6)x 3 4 5 6 7 8
p(x) .15 .3 .25 .18 .1 .02

mean=(3)(.15)+(4)(.3)+(5)(.25)+(6)(.18)+(7)(.1)+(8)(.02)=4.8
variance=(3sq)(.15)+(4sq)(.3)+(5sq)(.25)+(6sq)(.18)+(7sq)(.1)+(8sq)(.02)=25.06 - (4.8) sq=2.0
sd= the square root of 2.0= 1.4

12)find expected profit per month:
#jobs 1 2 3 4
probability .2 .3 .4 .1

e(x)=(1)(.2)+(2)(.3)+(3)(.4)+(4)(.1)=2.4 this show to use same formula as the mean I used
on the above problems.


Thak you for your help, just want to make sure im doing this all right!
 
MRS.FREE said:
can someone please just look over this and make sure im on the right track. thank you! (i didn;t know how to put the squared symbol in so i just typed "sq"...sorry)

2)
x 19 20 21 22 23
p(x) .2 .2 .3 .2 .1

mean=(1.9)(.2)+(20)(.2)+(21)(.3)+(22)(.2)+(23)(.1)=20.8
variance=(19sq)(.2)+(20sq)(.2)+21sq)(.3)+(22sq)(.2)+(23sq)(.1)=434.2 - (20.8)sq=1.6
sd=the sq root of 1.6=1.3

*HOW MANY SHIRTS THE MANAGER PURCHASE IF HE WANTS TO MAKE SURE HE HAS ENOUGH SHIRTS FOR THE NEXT 5 DAYS?
i don't understand how to answer this....PLEASE HELP WITH THIS PART! :)

What are 'x' and 'p(x)' - in other words how are those related to purchasing shirts?

4)
x 5 6 7 8 9 10
x(p) .05 .2 .4 .1 .15 .1

What are 'x' and 'p(x)' or 'x(p)'
Click to expand...
 
#2) asys the number of suits sold per day at a retail store in shown in the table (x= number of suits sold, p(x)= probability) with the corresponding probabilities. find the mean, variance, standard deviation, of the distribultion...

sorry i should of put what it said, and when i typed it the x's lined up with the p(x0's below them but when i posted it they kida shifted...

4)the probability that a player will get 5 to 10 questions right on a trivia quiz are shown below. find the mean, variance, sd for the distribution.

6) the local animal shelter adopts out cats and dogs each week with the following probability.

12) a landscaper bids on jobs where he can make $3000 profit. the probability of getting 1,2,3, or 4 jobs per month are shown.



the charts i put in the first post correspond to these...sorry again and ty so much for your help!
 
LET ME TRY THIS AGAIN, HERE ARE THE WORD PROBLEMS TOO, SORRY!
ALSO, CAN SOMEONE LOOK AT THE RED TEXT IN THE FIRST PROBLEM, I DON'T UNDERSTAND HOW TO GET THAT PART. THANK YOU!

can someone please just look over this and make sure im on the right track. thank you! (i didn't know how to put the squared symbol in so i just typed "sq"...sorry)

2) the number of suits sold per day at a retail store in shown in the table (x= number of suits sold, p(x)= probability) with the corresponding probabilities. find the mean, variance, standard deviation, of the distribution...
x 19 20 21 22 23
p(x) .2 .2 .3 .2 .1

mean=(1.9)(.2)+(20)(.2)+(21)(.3)+(22)(.2)+(23)(.1)=20.8
variance=(19sq)(.2)+(20sq)(.2)+21sq)(.3)+(22sq)(.2)+(23sq)(.1)=434.2 - (20.8)sq=1.6
sd=the sq root of 1.6=1.3

*HOW MANY SHIRTS SHOULD THE MANAGER PURCHASE IF HE WANTS TO MAKE SURE HE HAS ENOUGH SHIRTS FOR THE NEXT 5 DAYS?
I don't understand how to answer this....PLEASE HELP WITH THIS PART!

4) The probability that a player will get 5 to 10 questions right on a trivia quiz is shown below. Find the mean, variance, sd for the distribution.
x 5 6 7 8 9 10
p(x) .05 .2 . 4 .1 .15 .1

mean=(5)(.05)+(6)(.2)+(7)(.4)+(8)(.1)+(9)(.15)+10)(.1)=7.4
variance=(5sq)(.05)+(6sq)(.2)+(7sq)(.4)+(8sq)(.1)+(9)(.15)+(10)(.1)=56.6 - (7.4)sq=1.8
sd=the sq root of 1.8=1.3



6) The local animal shelter adopts out cats and dogs each week with the following probability.
x 3 4 5 6 7 8
p(x) .15 .3 .25 .18 .1 .02

mean=(3)(.15)+(4)(.3)+(5)(.25)+(6)(.18)+(7)(.1)+(8)(.02)=4.8
variance=(3sq)(.15)+(4sq)(.3)+(5sq)(.25)+(6sq)(.18)+(7sq)(.1)+(8sq)(.02)=25.06 - (4.8) sq=2.0
sd= the square root of 2.0= 1.4

12) a landscaper bids on jobs where he can make $3000 profit. the probability of getting 1,2,3, or 4 jobs per month are shown. find expected profit per month:
#jobs (X) 1 2 3 4
prob P(X) .2 .3 .4 .1

e(x)=(1)(.2)+(2)(.3)+(3)(.4)+(4)(.1)=2.4
this show to use same formula as the mean I used
on the above problems.


Thank you for your help, just want to make sure I’m doing this all right!
 
MRS.FREE said:
LET ME TRY THIS AGAIN, HERE ARE THE WORD PROBLEMS TOO, SORRY!
ALSO, CAN SOMEONE LOOK AT THE RED TEXT IN THE FIRST PROBLEM, I DON'T UNDERSTAND HOW TO GET THAT PART. THANK YOU!

can someone please just look over this and make sure im on the right track. thank you! (i didn't know how to put the squared symbol in so i just typed "sq"...sorry)

2) the number of suits sold per day at a retail store in shown in the table (x= number of suits sold, p(x)= probability) with the corresponding probabilities. find the mean, variance, standard deviation, of the distribution...
x 19 20 21 22 23
p(x) .2 .2 .3 .2 .1

mean=(1.9)(.2)+(20)(.2)+(21)(.3)+(22)(.2)+(23)(.1)=20.8
variance=(19sq)(.2)+(20sq)(.2)+21sq)(.3)+(22sq)(.2)+(23sq)(.1)=434.2 - (20.8)sq=1.6
sd=the sq root of 1.6=1.3

*HOW MANY SHIRTS SHOULD THE MANAGER PURCHASE IF HE WANTS TO MAKE SURE HE HAS ENOUGH SHIRTS FOR THE NEXT 5 DAYS?
I don't understand how to answer this....PLEASE HELP WITH THIS PART!

"make sure" - without a confidence level - is an ambiguious word, and does mean much in statistics. That is why I assume no body wanted to answer this question. Theoretically, s/he can never have enough shirt to be 100% sure (p = 1) that s/he will not run out.

4) The probability that a player will get 5 to 10 questions right on a trivia quiz is shown below. Find the mean, variance, sd for the distribution.
x 5 6 7 8 9 10
p(x) .05 .2 . 4 .1 .15 .1

mean=(5)(.05)+(6)(.2)+(7)(.4)+(8)(.1)+(9)(.15)+10)(.1)=7.4
variance=(5sq)(.05)+(6sq)(.2)+(7sq)(.4)+(8sq)(.1)+(9)(.15)+(10)(.1)=56.6 - (7.4)sq=1.8
sd=the sq root of 1.8=1.3



6) The local animal shelter adopts out cats and dogs each week with the following probability.
x 3 4 5 6 7 8
p(x) .15 .3 .25 .18 .1 .02

mean=(3)(.15)+(4)(.3)+(5)(.25)+(6)(.18)+(7)(.1)+(8)(.02)=4.8
variance=(3sq)(.15)+(4sq)(.3)+(5sq)(.25)+(6sq)(.18)+(7sq)(.1)+(8sq)(.02)=25.06 - (4.8) sq=2.0
sd= the square root of 2.0= 1.4

12) a landscaper bids on jobs where he can make $3000 profit. the probability of getting 1,2,3, or 4 jobs per month are shown. find expected profit per month:
#jobs (X) 1 2 3 4
prob P(X) .2 .3 .4 .1

e(x)=(1)(.2)+(2)(.3)+(3)(.4)+(4)(.1)=2.4
this show to use same formula as the mean I used
on the above problems.


Thank you for your help, just want to make sure I’m doing this all right!
Click to expand...

As far as I can tell, your work looks correct.
 
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