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How to choose caliper for propensity score matching?
When estimating differences in means or risk differences, we recommend that researchers match on the logit of the propensity score using calipers of width equal to 0.2 of the standard deviation of the logit of the propensity score.
What is a caliper width?
The caliper width defines the range within which the propensity scores (or logit of the propensity scores) must fall to be considered a valid match [13].
What is a calliper used for?
Caliper, also spelled calliper, measuring instrument that consists of two adjustable legs or jaws for measuring the dimensions of material parts.
What are car calipers?
Calipers are found on each wheel and work to squeeze the brake pads against the rotors in an effort to slow the spin of the wheel and get the vehicle to reduce its speed. When the brake pedal is pressed, it forces hydraulic pressure on the pistons in the calipers to force the pads against the rotors.
What is psmatch2?
psmatch2 stores the estimate of the standard error of the ATT in r(seatt) or with more than one outcome variable, in r(seatt_varname). With more than one outcome variable the effects are returned as r(att_varname) etc. for each outcome variable and effect.
What is common support?
Common support is subjectively assessed by examining a graph of propensity scores across treatment and comparison groups (Figure 1). A starting test of balance is to ensure that the mean propensity score is equivalent in the treatment and comparison groups within each of the five quintiles (Imbens 2004).
What are the 4 types of calipers?
There are 8 different types of caliper available today. These include: inside caliper, outside caliper, divider caliper, oddleg caliper, micrometer caliper, Vernier caliper, dial caliper, and digital caliper. Inside calipers are used, as the name implies, to measure the interior of a part.
Why is a narrower caliper better for propensity scores?
A tighter caliper led to greatly reduced bias and closer matches, although some subjects could not be matched. This study suggests that a narrow caliper can improve the performance of propensity score matching.
How is a caliper used in a simulation?
This study used simulations to explore the effects of these decisions on both the imbalance of covariates and the closeness of matching, while allowing the numbers of potential matches and strengths of association between the confounding variable and the exposure to vary.
When to use a covariate balance or caliper?
caliper, covariate balance, matching, propensity score. Propensity score matching is widely used in epidemiologic observational studies to reduce bias in estimates of the effect of an exposure due to confounding by indication.
Can a caliper be used to reduce bias?
Use of the recommended caliper reduced the bias considerably, but bias remained if subjects were selected by increasing or decreasing propensity score. A tighter caliper led to greatly reduced bias and closer matches, although some subjects could not be matched.