A level Statistics doubt??Post your doubts here!

[prekshya]

s-12-62 ques num 2.i. help please

 

[sma786]

http://papers.xtremepapers.com/CIE/...AS Level/Mathematics (9709)/9709_s04_qp_6.pdf Question 4, (ii) ! Help please?

 

[syed1995]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s04_qp_6.pdf Question 4, (ii) ! Help please?

This was a long question!

0.2025 = small from part i...

and according to question the rest are divided equally

so medium+large=1-0.2025
medium+large=0.7975
2x=0.7975 since both are same...
x=0.39875

so for large (as well as medium) the probability will be 0.39875

Now let's take large since they asked for large...

P(X>u)=0.39875
P(z>(u-450/120)=0.39875
z<-(u-450/120)=inversePhi(0.39875)
z<-(u-450/120)=-invPhi(1-0.39875)
z<-(u-450/120)=-invPhi(1-0.39875)
u-450/120=invPhi(0.60125)
u-450/120=0.256
u-450=30.72
u=480.72
u=481 3sf..

the weight above which they are classified as large is 481 Answer... Is that correct?

 

[A star]

This was a long question!

0.2025 = small from part i...

and according to question the rest are divided equally

so medium+large=1-0.2025
medium+large=0.7975
2x=0.7975 since both are same...
x=0.39875

so for large (as well as medium) the probability will be 0.39875

Now let's take large since they asked for large...

P(X>u)=0.39875
P(z>(u-450/120)=0.39875
z<-(u-450/120)=inversePhi(0.39875)
z<-(u-450/120)=-invPhi(1-0.39875)
z<-(u-450/120)=-invPhi(1-0.39875)
u-450/120=invPhi(0.60125)
u-450/120=0.256
u-450=30.72
u=480.72
u=481 3sf..

the weight above which they are classified as large is 481 Answer... Is that correct?

yup but u know u really are a whiz i didnt write an answer cause me too lazy

 

[kiara15]

http://www.ilovemaths.com/3.asp ... very useful link

 

[kiara15]

i had some ambiguity in below quest:
1) P(Z>a)=0.8888 , a is negativ,
1-fi(-a)=o.8888
1-[1-fi(a) ]=o.8888
the other solution of quest i found:
2)p(z<t)=0.25, t is negativ
fi(-t)=0.25
1-fi(t)=0.25..
can anyone tell me this difference and concept how to solve such type of quest plzzz

 

[daredevil]

Can u fill up this table for me?? I am not getting how the answer is as it is >_<

 

[daredevil]

Link

s-12-62 ques num 2.i. help please

 

[shafayat]

Can u fill up this table for me?? I am not getting how the answer is as it is >_<

HI man ..
I am sorry I am not real neat with my work ..
but how I like to do these questions is by making a two way table like in the image ..
draw the table as first dice and second dice ... then inside write only what question says ! like its the lower value of the two numbers .. and also if its the same number on both dice then he writes the number on one of the dices .. sooo u just complete the table like 1,1 the answers are same so the result he wud write is 1 ,,, den 1,2 the lower result is two ! so like that we fill the table ..
then to write the probabilities we just count the number of 1'ns in the table and divide by the total number of solutions that is 36 here ! ( the total number of answers u got IN the table ) then we count 2's and write .. same way for others !!

the table wud be
11/36 , 9/36 , 7/36 , 5/36 , 3/36 , 1/36

,
.
please correct me if I am wrong .. hope I cud help

 

[airyhat]

3i) z value for .9 = 1.282
as .9 is for probability of >5.2
z= -1.282
so, 5.2 - 3σ/σ = -1.282
σ = 7.24

ii) For this part the range is 1 standard deviation from the mean:
so the range of z value should be -1<z<1
ϕ1 - (1-ϕ1)
= .8413 - 1 +.8413
= .683

Number of observations = .683* 800 = 546.4

I dont understand part ii

 

[A star]

Can u fill up this table for me?? I am not getting how the answer is as it is >_<

easy way to solve these type of question draw a probability distribution table . it will show you all 36 probabilities then all you have to do is copy and write down

 

[A star]

HI man ..
I am sorry I am not real neat with my work ..
but how I like to do these questions is by making a two way table like in the image ..
draw the table as first dice and second dice ... then inside write only what question says ! like its the lower value of the two numbers .. and also if its the same number on both dice then he writes the number on one of the dices .. sooo u just complete the table like 1,1 the answers are same so the result he wud write is 1 ,,, den 1,2 the lower result is two ! so like that we fill the table ..
then to write the probabilities we just count the number of 1'ns in the table and divide by the total number of solutions that is 36 here ! ( the total number of answers u got IN the table ) then we count 2's and write .. same way for others !!

the table wud be
11/36 , 9/36 , 7/36 , 5/36 , 3/36 , 1/36

,
.
please correct me if I am wrong .. hope I cud help

yup correct . lol it amazez me how can you all write long answers :O

 

[felicia tan]

question 3 (ii) http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_w09_qp_61.pdf
how do you solve this?

 

[panoramafolks]

question 3 (ii) http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_w09_qp_61.pdf
how do you solve this?

sorry i m not neat!

 

[panoramafolks]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s09_qp_6.pdf
question 4?

 

[syed1995]

i had some ambiguity in below quest:
1) P(Z>a)=0.8888 , a is negativ,
1-fi(-a)=o.8888
1-[1-fi(a) ]=o.8888
the other solution of quest i found:
2)p(z<t)=0.25, t is negativ
fi(-t)=0.25
1-fi(t)=0.25..
can anyone tell me this difference and concept how to solve such type of quest plzzz

P(z>a)=0.888
P(z<-a)=0.888
Phi(-a)=0.888
1-Phi(a)=0.888
Phi(a)=0.112
a=invPhi(0.112)
a=-invPhi(1-0.112)
a=-invPhi(0.888)

and the second one ..

(z<t)=0.25
Phi(t)=0.25
t=invPhi(0.25)
t=-invPhi(1-0.25)
t=-invPhi(0.75)

 

[syed1995]

1!+4! is not equal to 5! :\

 

[panoramafolks]

1!+4! is not equal to 5! :\

it is ... not after calculation but b4 that... its what my sir taught

 

[syed1995]

it is ... not after calculation but b4 that... its what my sir taught

you will only confuse people with that.. it's adding an entire block.. you should write it as (1+4)! not 1!+4!

 

[Soldier313]

Aoa wr wb
Can someone please tell me, how do we know when we have to use what value
eg for this qn, how do we know it's 5 rather than 4.5 rather than 4.5 etc




PS: I know HOW to solve the qn, ie the method and all, my only doubt is how do we know the value to use (as mentioned above)

Thank you