VCE Methods Question Thread!

[keltingmeith]

Thanks EulerFan101 

Say if it was a 1 mark question and you have to give a reason why they chose that particular value of m.
What would you say?

working
But, a<X<b
.: answer

What influences if a distribution is symmetrical out of these and how?

Median or Mode or Mean

This is not covered in methods - at all. But, a particular distribution is said to be symmetric if there is an x such that:


where f is the probability function (be it density or mass) of the random variable. In this situation, it is said that the random variable is symmetrical around x.

A consequence of this definition is that if the mean and the median of the random variable are both equal, then the distribution is symmetric. Further, the mean and median both equal to x. The proof for this is a bit beyond VCE level.

[MightyBeh]

Hey guys! Just wondering if you could talk me through how to simplify the equations on the attached document.

Thanks! 

I can't download it right now to help because there's something silly going on with AN's attachments (or, this one at least). It'd be great if you emailed it to me or posted pictures or something else instead.

[knightrider]

working
But, a<X<b
.: answer

This is not covered in methods - at all. But, a particular distribution is said to be symmetric if there is an x such that:

(Image removed from quote.)
where f is the probability function (be it density or mass) of the random variable. In this situation, it is said that the random variable is symmetrical around x.

A consequence of this definition is that if the mean and the median of the random variable are both equal, then the distribution is symmetric. Further, the mean and median both equal to x. The proof for this is a bit beyond VCE level.

Thanks EulerFan101 

where you have written But, a<X<b

are a and b the endpoints of the domain?

[keltingmeith]

Thanks EulerFan101 

where you have written But, a<X<b

are a and b the endpoints of the domain?

a and b are the smallest and largest values that X can take on - i.e., the endpoints of the domain of the pdf/pmf.

[knightrider]

a and b are the smallest and largest values that X can take on - i.e., the endpoints of the domain of the pdf/pmf.

thanks EulerFan101 

whats a pmf?

[silverpixeli]

thanks EulerFan101 

whats a pmf?

probability mass function (another name for a probability density function, which is the term usually used in methods in my experience)

[knightrider]

Are we required to know this for methods (attached )?

[silverpixeli]

Are we required to know this for methods (attached )?

Nope, it's not mentioned in the study design (in the Methods sections - it is a further concept) and I've definitely never seen it tested.

(But it's not an incredibly tricky concept, it's very similar to the median, except you're dealing with the section that has 25% of the area below and 25% above. This definition gives you the width of that section, which can be another way of measuring the spread of a distribution, rather than using variance or standard deviation!)

[knightrider]

Nope, it's not mentioned in the study design (in the Methods sections - it is a further concept) and I've definitely never seen it tested.

(But it's not an incredibly tricky concept, it's very similar to the median, except you're dealing with the section that has 25% of the area below and 25% above. This definition gives you the width of that section, which can be another way of measuring the spread of a distribution, rather than using variance or standard deviation!)

Thanks silverpixeli 

[knightrider]

How come when i antidifferentiate by hand i get

but when i  antidifferentiate using the CAS i get  ?

I am using the casio classpad 400.

Does anyone know whats wrong with my CAS?

Thanks 

[keltingmeith]

probability mass function (another name for a probability density function, which is the term usually used in methods in my experience)

Yeah, my bad - the two are different (for reasons not exactly relevant to methods, but fun fact: a pdf can be defined for discrete random variables, a pmf cannot be defined for continuous random variables. It's not particularly easy, and DEFINITELY beyond VCE level, but the more you know~), but it's such a small thing that I wasn't aware it's not in the study design... (another fun fact, it is in the new one)

Sorry for any confusion. n.n;

How come when i antidifferentiate by hand i get

but when i  antidifferentiate using the CAS i get  ?

I am using the casio classpad 400.

Does anyone know whats wrong with my CAS?

Thanks 

Not many people on here are versed in the classpad - you should ask your teacher. However, if you're just calculating an integral, it's not too much of an issue - they're doing the antidifferentation correct, but they're adding an actual constant instead of a "C". So, just take the constant term, replace it with c, and you've still got the correct answer.

[plato]

How come when i antidifferentiate by hand i get

but when i  antidifferentiate using the CAS i get  ?

I am using the casio classpad 400.

Does anyone know whats wrong with my CAS?

Thanks 

Try clearing all variables first.

[knightrider]

Yeah, my bad - the two are different (for reasons not exactly relevant to methods, but fun fact: a pdf can be defined for discrete random variables, a pmf cannot be defined for continuous random variables. It's not particularly easy, and DEFINITELY beyond VCE level, but the more you know~), but it's such a small thing that I wasn't aware it's not in the study design... (another fun fact, it is in the new one)

Sorry for any confusion. n.n;

Not many people on here are versed in the classpad - you should ask your teacher. However, if you're just calculating an integral, it's not too much of an issue - they're doing the antidifferentation correct, but they're adding an actual constant instead of a "C". So, just take the constant term, replace it with c, and you've still got the correct answer.

Thanks so much EulerFan101 

Try clearing all variables first.

Thanks for that plato. I have already tried that but it doesnt work.

[knightrider]

Are we required to know the binomial theorem for methods?

[keltingmeith]

Are we required to know the binomial theorem for methods?

Will they ask you specific questions on it? No.
Is it super useful for expanding/factorising and so something you should understand how to use given the time? Definitely.