Multiple regression works very well under some conditions. We ask: Are these conditions true in most real property valuations? This is actually a vast topic, so we can only reflect on some of the conditions or assumptions which are required for a multiple regression to be valid. Much (if not all) “advanced” appraiser education makes […]
Appraisers historically have been sold bogus franchises, software, and other magic solutions. Only $199.95 — Push the enchanted ‘calculate’ button and get ‘correct’ adjustments. Sounds good. It is nice to think that for this small charge, I can save hours and get the right, fully mathematical solution to an adjustment amount. I will be wonderful! […]
Time adjustments is a timely topic. Recent ski-jump rises in prices have been ramp-ant in many places. Valuemetrics.info provided a free, two-hour webinar on the topic, and we had almost exactly 1000 appraisers sign up. (Although many did not show – free, you know.) Prior to the webinar, I asked some reviewers about how appraisers […]
R² or r² is a number which has been squared. Or is it? It’s popular and feels sophisticated. Especially if it’s ‘high’. Higher is better. Or is it? There are actually a number of ‘fallacies’ around the use of R2 or r2. First let’s distinguish between the big letter R and the little letter r. […]
Recent presentations and articles on “Big Data and Appraisal” universally say that big changes in technology and analytics are affecting appraisal. What I don’t hear is: What can I do about it? Will I be able to work in five years? Will our appraisal organizations be around? If there is a place for me, what […]
We are taught that a comp should be similar, then we make adjustment. Easy. There are three types of adjustment results. Some are exact, others are approximate, and others are biased but can help us get near the right adjustment number. It is important to understand the basic differences in these three different outcomes. We […]
Why is it so easy? Why is it so hard? [Author’s Note: At last year’s joint AI and AI Canada conference in June, 2017, in Ottawa. my talk was titled, Common Regression Errors and Mistakes.] Regression is nothing but a mathematical formula. How can it be wrong? Not all that complicated actually – find the slope […]
Statistics are infernal for a few basic reasons. Misuse of words. Using different meanings at different times. (Like ‘infer’); Assume a clever tool will give you a clever answer (like regression); The fallacy that inferential statistics works without random sampling; The worst fallacy that regression is always based on an inferential sampling process. Let’s look […]
Regression is just a math formula. Regression is not magic. The answer is only as good as the data used. Regression is a tool. It is helpful to understand the difference between a tool and a model. To build a house, you need a hammer, the tool. You also need a nailing schedule, which tells you […]