It is confusing isn't it?
Prop is right when he refers to different methodologies- I like Residex and have been referring to their growth figures for over 10 yrs now myself. Residex actually won an international actuarial award for their "Dwelling Price Trading Index" method, which they currently use in their quarterly reports- quite different from the simpler methods used by others to generate data.
However every method is flawed and statistics can be skewed by such factors such as new developments (creating a "false" impression of improved growth or median values) lack of sufficient sales to generate a reliable median, high amounts of renovated properties in one suburb compared to another etc. There's lots of variables, hence the need to not solely rely on growth figures (and, in particular, rental yields) when making a decision on where and what to buy. Obviously local knowledge is paramount (down to street level in some suburbs/towns) as is current activity. I also like the Reno Kings philosophy of "following the infrastructure"- even in an established area new projects such as transport links, increased parking stations, schools, community spaces etc can add value to property.