Wednesday
10Mar2010

It might just be worse than that

DateWednesday, March 10, 2010 at 10:39AM | AuthorStu | CommentPost a Comment

I rarely get to blog here, so I am taking the opportunity to point out something above the general decline in mathematics students - the losing of knowledge.

Take a look at these feeds from the Australian:

Mathematics Students in Serious Decline

Equation for maths warns of disaster

I was teaching at University when we as a society ripped these students off, replacing core problem solving with vapid histories and philosophies. Such a change had a lot to do with the academia of mathematics becoming disconnected with the application of its theory. And this is where the problem lies.

I’ll give you an example. I sought to take a Graduate Certificate in Applied Statistics recently. Not because I wanted another piece of paper, but because I am looking for some more knowledge to protect myself and my clients from stupid misapplications of theory. I couldn’t find one that was more than a simple training course in certain statistical software packages. Needless to say, I haven’t enrolled. I need, as do all analysts more than the mindless application of a software package.

The need arose when the tried and proven ANOVA test failed on me. ANOVA is the draught horse of multiple testing applications. I had a test returning p values that experience tells were way too small. The underlying data, was violating a number of assumptions of the ANOVA test, and I could find a transform that would fix it. I still haven’t found a transform, and have had to move on without that test, making my story that much longer as I now have to justify the use of “unorthodox” testing procedures.

This is not the first time that I’ve come across underlying short-comings in standard procedures. My argument comes from the fact that often I have to go right back to 1930’s papers by deities like Fisher, or early works by Tukey to find underlying mechanics and discussions. Far too many papers simply state the software package they used, and the outcomes, never addressing whether the package should have been applied in the first place.

I wonder how often it is that an assumption has been made regarding validity, and never checked.

| | Print ArticlePrint Article
in
Tuesday
23Feb2010

Join us for a cuppa at the Clean Energy Council Conference

DateTuesday, February 23, 2010 at 4:58PM | Authoradmin | CommentPost a Comment

Symbolix is proud to be a sponsor of the upcoming Clean Energy Council National Conference.  It’s being held in Adelaide from the 3rd-5th May 2010. 

The conference is attended by over 700 delegates from all areas of the clean energy sector, and promises some interesting discussion and insight.

We’ll be there throughout, and are sponsoring a break time on Tuesday, so drop down to the exhibition hall and have a coffee on us.

| | Print ArticlePrint Article
in ,
Monday
01Feb2010

The median stripped bare? Well....

DateMonday, February 1, 2010 at 9:20AM | Authoradmin | Comment3 Comments

The Age newspaper today published an article analysing differences in the way different market research companies report the median selling price for different suburbs.  This is an important point to discuss, but I was not concerned by the analysis as much as this definition of median:

“However, it is worth keeping in mind that the median price is not the same as thing as the average price. It is simply the middle sale price when all property sales are arranged chronologically.”

Um, no actually.  For a given month, the middle sale price when sales are arranged chonologically (in time) would be the price received around the 15th of the month (assuming an even sales rate through the month).

For the record, here are the definitions you need.  When we talk “average” we may mean one of three measures.

  • The median is the middle value, when prices are arranged in order from lowest to highest.
  • The mean (most commonly just called the average) is just the sum of all the prices, divided by the number of sales.
  • The mode is the most common sale price. 

In many cases, these three measures are very similar, but not always.

It’s worth noting that the mean is highly susceptible to outliers - a one off $10 million dollar property sale will inflate the mean price, but leave the median less affected.  This is why the median is a more stable measure of things like house prices, which are likely to have a number of small outliers (very low or very high prices).

Now that’s settled, the rest of the article is worth reading - it discusses why understanding the drivers behind changes in these measures is so important.  For example, if a jump in median house prices reflects a drive by investors moving on high end properties, it does not necessarily translate to making a killing on selling a low end property to a young first buyer market.

This is important to think about, but the first step is to understand the basics of what the measures actually mean.

| | Print ArticlePrint Article
in ,
Page 1 2 3 4 5 ... 12 Next 3 Entries ยป