A level Statistics doubt??Post your doubts here!

[MustafaMotani]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_w11_qp_61.pdf Q5 part ii why havent they subtracted one from final answer MustafaMotani

coz 13 < 20 meaning that z value will be negative ...
P(z>-a) = p(z<a)

 

[A star]

n=250
p =0.86
np=250*0.86=215>5
nq=259*0.14=35>5
mean=250*0.86=215
var=npq=30.1
X is a normal distribution of(215, 30.1)
P(X>210)
so applying continuity corrections,
P(Z>210.5-215/root(30.1))
=P(Z>-0.8202)
=0.794

y havent you subtracted the answer from 1?

 

[A star]

coz 13 < 20 meaning that z value will be negative ...
P(z>-a) = p(z<a)

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_w11_ms_61.pdf http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_w11_qp_61.pdf

and check its part i ms is the ans correct?

 

[x-gamer-x]

coz 13 < 20 meaning that z value will be negative ...
P(z>-a) = p(z<a)

plz solve this and explain
The volume of milk in millilitres in cartons is normally distributed with mean µ and standard deviation
8. Measurements were taken of the volume in 900 of these cartons and it was found that 225 of them
contained more than 1002 millilitres. Calculate the value of µ.

 

[MustafaMotani]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_w11_ms_61.pdf http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_w11_qp_61.pdf

and check its part i ms is the ans correct?

yes'

 

[MustafaMotani]

plz solve this and explain
The volume of milk in millilitres in cartons is normally distributed with mean µ and standard deviation
8. Measurements were taken of the volume in 900 of these cartons and it was found that 225 of them
contained more than 1002 millilitres. Calculate the value of µ.

ohk wait ..

 

[Alice123]

y havent you subtracted the answer from 1?

cuz the ans is negative
see
P(Z>-0.8202)
this cn b written as
1-P(-0.8202)
=1-[1-P(0.8202)] (the 1s canel n the - becomes +)
=P(0.8202)

 

[A star]

You have to use the normal approximation.
You'll need the mean and the sd.
Mean= np= 250*0.86=215
sd= sqrt of npq= sqrt( 250*0.86*0.14)= 5.48

Then standardize 210.5 to get a z value
Z= (210.5-215)/5.48
=-( -0.820)

The value which corresponds to this value is 0.7934

i got the answer but was confused that y didnt we subtract the answer from one

 

[A star]

yes'

y did they take value of phiinverse(0.97) not phi inverse (0.94) given in the question

 

[A star]

cuz the ans is negative
see
P(Z>-0.8202)
this cn b written as
1-P(-0.8202)
=1-[1-P(0.8202)] (the 1s canel n the - becomes +)
=P(0.8202)

thankyou

You have to use the normal approximation.
You'll need the mean and the sd.
Mean= np= 250*0.86=215
sd= sqrt of npq= sqrt( 250*0.86*0.14)= 5.48

Then standardize 210.5 to get a z value
Z= (210.5-215)/5.48
=-( -0.820)

The value which corresponds to this value is 0.7934

 

[MustafaMotani]

plz solve this and explain
The volume of milk in millilitres in cartons is normally distributed with mean µ and standard deviation
8. Measurements were taken of the volume in 900 of these cartons and it was found that 225 of them
contained more than 1002 millilitres. Calculate the value of µ.

 

[MustafaMotani]

y did they take value of phiinverse(0.97) not phi inverse (0.94) given in the question

see the pic u may get it ..

 

[salvatore]

plz someone do this

The volume of milk in millilitres in cartons is normally distributed with mean µ and standard deviation
8. Measurements were taken of the volume in 900 of these cartons and it was found that 225 of them
contained more than 1002 millilitres. Calculate the value of µ.

The probability of getting more than 1002mm, P(X>1002), is 225/900 = 1/4
Therefore, P(X < 1002) = 1 - 1/4 = 0.75

From the probability table, z = 0.674 (When probability is 0.75).

Standaridising,
(1002 - µ)/8 = 0.674

After doing the calculations, you'll get µ = 997.

Hope that helped

 

[MustafaMotani]

plz solve this and explain
The volume of milk in millilitres in cartons is normally distributed with mean µ and standard deviation
8. Measurements were taken of the volume in 900 of these cartons and it was found that 225 of them
contained more than 1002 millilitres. Calculate the value of µ.

lol sorry i did the wrong question .. xD wait i ll do yours as well.

 

[Freaked out]

http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_w09_qp_62.pdf
can somebody solve Q1

 

[Alice123]

https://www.xtremepapers.com/community/posts/478490/
see phyZac's post.. u'll understand in secs

(20+12<x<20-12)

now you have to imagine the graph in your head, and you have to come into a conclusion that it is symmetrical.

Now imagine the z of 20+12 that is 32 is x
So the z of 20-12 that is 8 will be a negative number -x

Both of them are x but one is negative, because they are the same distance from the mean

Let the probability of x is p
so the probability of -x is 1-p

we know that difference of the two probability is 0.94

so p - (1-p) = 0.94
p - 1 + p = 0.94
2p = 0.95 + 1 = 1.94
p = 0.97

Now is p is 0.97 z is from the table, 1.882 (or 1.881)

now continue normally

1.882 = 32-20 / sd
sd = 12/1.882
=6.38
A star

 

[MustafaMotani]

plz solve this and explain
The volume of milk in millilitres in cartons is normally distributed with mean µ and standard deviation
8. Measurements were taken of the volume in 900 of these cartons and it was found that 225 of them
contained more than 1002 millilitres. Calculate the value of µ.

 

[Alice123]

You have to use the normal approximation.
You'll need the mean and the sd.
Mean= np= 250*0.86=215
sd= sqrt of npq= sqrt( 250*0.86*0.14)= 5.48

Then standardize 210.5 to get a z value
Z= (210.5-215)/5.48
=-( -0.820)

The value which corresponds to this value is 0.7934

please see my post in the mathematics thread

 

[A star]

(20+12<x<20-12)

now you have to imagine the graph in your head, and you have to come into a conclusion that it is symmetrical.

Now imagine the z of 20+12 that is 32 is x
So the z of 20-12 that is 8 will be a negative number -x

Both of them are x but one is negative, because they are the same distance from the mean

Let the probability of x is p
so the probability of -x is 1-p

we know that difference of the two probability is 0.94

so p - (1-p) = 0.94
p - 1 + p = 0.94
2p = 0.95 + 1 = 1.94
p = 0.97

Now is p is 0.97 z is from the table, 1.882 (or 1.881)

now continue normally

1.882 = 32-20 / sd
sd = 12/1.882
=6.38
A star

i am guessing only math wizes got this question right though its common sense but difficult to understand

 

[x-gamer-x]

The probability of getting more than 1002mm, P(X>1002), is 225/900 = 1/4
Therefore, P(X < 1002) = 1 - 1/4 = 0.75

From the probability table, z = 0.674 (When probability is 0.75).

Standaridising,
(1002 - µ)/8 = 0.674

After doing the calculations, you'll get µ = 997.

Hope that helped

thanks bro