VCE General & Further Maths Question Thread!

[minerva]

Hi, could someone please explain "Correcting for seasonlity"? I don't understand how or why it's used.
Here's a question I'm stuck on:
The seasonal index of January is 1.2 and the actual sales figure is 9.6.
To correct the actual monthly sales figure for seasonality we need to:
A) decrease the actual sales figures by around 20%
B) increase the actual sales figures by around 20%
C) decrease the actual sales figures by around 17%
D) increase the actual sales figures by around 17%
E) increase the actual sales figures by around 80%

Thanks in advance

[Peanut Butter]

Hi, could someone please explain "Correcting for seasonlity"? I don't understand how or why it's used.
Here's a question I'm stuck on:
The seasonal index of January is 1.2 and the actual sales figure is 9.6.
To correct the actual monthly sales figure for seasonality we need to:
A) decrease the actual sales figures by around 20%
B) increase the actual sales figures by around 20%
C) decrease the actual sales figures by around 17%
D) increase the actual sales figures by around 17%
E) increase the actual sales figures by around 80%

Thanks in advance

"To correct for seasonality" means to basically get a seasonal index of one. So you want to go from 1.2 to 1. Since the SI is getting lower, it must be decreasing (therefore the answer has to be either a or c).

To figure out the percentage:

(1.2-1)/1.2 * 100 = 17 %

That formula ^ is pretty much the difference in seasonal indices over the original seasonal index. Does that make sense?

[minerva]

"To correct for seasonality" means to basically get a seasonal index of one. So you want to go from 1.2 to 1. Since the SI is getting lower, it must be decreasing (therefore the answer has to be either a or c).

To figure out the percentage:

(1.2-1)/1.2 * 100 = 17 %

That formula ^ is pretty much the difference in seasonal indices over the original seasonal index. Does that make sense?

Yes, thanks!!
Btw, I'm just fangirling over your 50 raw, haha. Congrats and thanks for that post on your Further experience and advice. Much appreciated.

[kingy123]

Hey could someone please tell me if by smoothing the time series, do we try to remove seasonality and random fluctuations in the time series, or just the random fluctuations?

Any help would be great

[clarke54321]

Hey could someone please tell me if by smoothing the time series, do we try to remove seasonality and random fluctuations in the time series, or just the random fluctuations?

Any help would be great

Hi Kingy,

Yes the aim is to diseasonalise the data to try and uncover some sort of trend. Therefore in doing this we are removing random fluctuations.

I hope this helps 

[knightrider]

How does the lack of a clear pattern in a  residual plot support the assumption that the relationship between the RV AND EV is linear?

[clarke54321]

How does the lack of a clear pattern in a  residual plot support the assumption that the relationship between the RV AND EV is linear?

Hey,

I can't give you a very technical answer, but if there was a clear pattern (such as a U-shaped curve) it would suggest that the points would be better suited to a non-linear model.

Check out this website, it explains it better than I can  : http://stattrek.com/statistics/dictionary.aspx?definition=Residual%20plot

[clarke54321]

Hi Everyone,

Could you please help me with the following questions relating to finance 

Thanks in advance

[knightrider]

Hey,

I can't give you a very technical answer, but if there was a clear pattern (such as a U-shaped curve) it would suggest that the points would be better suited to a non-linear model.

Check out this website, it explains it better than I can  : http://stattrek.com/statistics/dictionary.aspx?definition=Residual%20plot

Thanks clarke54321   

[AngelWings]

How does the lack of a clear pattern in a  residual plot support the assumption that the relationship between the RV AND EV is linear?

I can't give you a very technical answer, but if there was a clear pattern (such as a U-shaped curve) it would suggest that the points would be better suited to a non-linear model.

Check out this website, it explains it better than I can  : http://stattrek.com/statistics/dictionary.aspx?definition=Residual%20plot

Just an addition to Clarke54321's post quoted above, 'randomness' is generally needed to cancel out positive and negative residuals, as such, a +5 residual would be cancelled out by a -5 residual and so forth.

[knightrider]

Just an addition to Clarke54321's post quoted above, 'randomness' is generally needed to cancel out positive and negative residuals, as such, a +5 residual would be cancelled out by a -5 residual and so forth.

Thanks AngelWings 

[chenay0123]

Hi, can someone please explain how to do this recursion question? I don't get how you can go from u(n+1) to u(n-1). Thank you

[plato]

I think this is a misprint if the answer is meant to be E.
I think it should read u_n+1 = 2u_n - 1

[death to the vcaa]

Hey guys, it would raeally be appreciated if you guys could tell me an estimated study score for these results:
Sacs: B+
Exam 1 A+
Exam 2: A+
So far, I am doing terribly for sacs but am doing really good for practice exams, but I have a weak cohort that will probably struggle in the exams but do alright on the sacs, meaning my ranking will be around 5-10 and my sacs will probably scale down. I would really just like to get an estimate on my study score. Hoping to get above 40. Btw, I am in year 10 so if I screw up further, do use think it would be worth me repeating it in year 11 along side methods 3/4?

Hey guys, it would raeally be appreciated if you guys could tell me an estimated study score for these results:
Sacs: B+
Exam 1 A+
Exam 2: A+
So far, I am doing terribly for sacs but am doing really good for practice exams, but I have a weak cohort that will probably struggle in the exams but do alright on the sacs, meaning my ranking will be around 5-10 and my sacs will probably scale down. I would really just like to get an estimate on my study score. Hoping to get above 40. Btw, I am in year 10 so if I screw up further, do use think it would be worth me repeating it in year 11 along side methods 3/4?

A % here would be better than "A+"

For example:

GA1: B+
GA2: 37/40 (A+)
GA3: 53/60 (A+)
This might scrape you a 40, probably 39-41

On the other hand
GA1: B+
GA2: 40/40 (A+)
GA3: 57/60 (A+)
This is most likely a 47-49

If you give us a mark out of 40 and 60 for the exams then it would be easier to estimate.

On the other question: Repeating further isnt much of a benefit. Its a highly competitive subject and chances are that the exam might be easier the next year and then even harder to get a better score.