Planned missing data designs in psychological research

The authors describe 2 efficiency (planned missing data) designs for measurement: the 3-form design and the 2-method measurement design. The 3-form design, a kind of matrix sampling, allows researchers to leverage limited resources to collect data for 33% more survey questions than can be answered by any 1 respondent. Power tables for estimating correlation effects illustrate the benefit of this design. The 2-method measurement design involves a relatively cheap, less valid measure of a construct and an expensive, more valid measure of the same construct. The cost effectiveness of this design stems from the fact that few cases have both measures, and many cases have just the cheap measure. With 3 brief simulations involving structural equation models, the authors show that compared with the same-cost complete cases design, a 2-method measurement design yields lower standard errors and a higher effective sample size for testing important study parameters. With a large cost differential between cheap and expensive measures and small effect sizes, the benefits of the design can be enormous. Strategies for using these 2 designs are suggested.     

Cigarette Smoking, Physical Activity, and the Health Status of College Students

Research has supported a negative correlation between cigarette smoking and exercise; however, the temporal nature of this association is not obvious. We modeled the relationships among smoking, exercise, and self-perceived health over time, within a college population. We collected 5 waves of data from 1,023 undergraduate students over a 14-month period. The results verified that smoking and exercise each made independent contributions in the prediction of health. Smoking was associated with reduced exercise over time, while no evidence was found for the reverse relationship. Our final mediation model demonstrates that smoking is related to poorer self-perceived health, and that this effect is partially mediated by the fact that smokers are less likely to engage in exercise.