What is the effect of a treatment on health outcomes? The real question is: can you be more specific? Researchers may measure the treatment effect a variety of ways. Sensible research questions include: What is the average effect of the treatment across all individuals? What is the average treatment effect only among those who received [...]
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Will missing data affect physician P4P scores?
The answer is yes, but maybe not as much as you may thought. A paper by Ryan and Bao use data from a randomized controlled trial (RCT) called IMPACT (Improving Mood-Promoting Access to Collaborative Treatment) to determine if errors in physician quality profiling are due mostly to random variation or missing data. For this report, [...]
Read the rest of this entry »Mahalanobis Distance
What is Mahalanobis distance? Most people know what Euclidean distance is…it is the shortest distance between any two points. In other words, its what we typically think of when we think of distance – the distance we would measure with a ruler, and the one given by the Pythagorean formula. Unlike Euclidean distance, Mahalanobis distance [...]
Read the rest of this entry »Kaplan-Meier Survival Curves
Survival analysis is used in many contexts. Some examples include: Medical research: fraction of patients living for a certain amount of time after treatment. Economics: length of time people remain unemployed after a job loss. Engineering: time until failure of machine parts. Ecology: how long fleshy fruits remain on plants before they are removed by [...]
Read the rest of this entry »Is my distribution normal?
How can you tell if you have a normal distribution? For instance, assume you have data on the results of a drug relative to a placebo. You know the mean and standard deviation of the data, but that does not necessarily imply that the data is distributed in a normal fashion. How can you do [...]
Read the rest of this entry »What are we weighting for?
Weighting has a number of uses. For instance, one can use weighting to estimate population sample statistics. The Panel Study of Income Dynamics (PSID) for instance oversamples households with low income. To get nationally mean values, one must reweight the PSID values, either using survey weights or matching to a nationally representative sample such as [...]
Read the rest of this entry »How Missing Data affects Physicians’ P4P Bonuses
Pay-for-performance programs often offer bonuses (or penalties) for physicians, hospitals and other providers based on the quality of care patients receive. Measuring quality of care, however, is often difficult. For chronic conditions, for instance, many patients eligible for outcome measures may be lost to follow-up. This issue can potentially affect provider evaluations and bonus payments. [...]
Read the rest of this entry »Reichenbach’s Common Cause Principle
How can you tell whether one event causes another? For instance, assume that you observe that when one event happens, another event is more likely to happen. For instance, when it rains the ground gets wet. Generally, rain will cause the ground to get wet. Use of umbrellas is also highly correlated with the ground [...]
Read the rest of this entry »Measuring Convergence
Is regional variation in healthcare spending converging or diverging over time? How would you know? How would you measure convergence? A paper by Panopoulou and Pantelidis (2013) answers just such a question. They define 3 types of convergence. These include beta convergence, sigma convergence, and stochastic convergence. I explain each one below.
Read the rest of this entry »What is the Negative Binomial Model?
Many research questions require healthcare economists to measure the effect of various patient, physician or market-level characteristics on specific health events. Oftentimes, these events are discrete in nature. For instance, doctor’s visits, ER visits, and hospitalizations are all discrete events. To properly estimate the effect of certain characteristics on a discrete event, count models are needed. The [...]
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