"Construct Validity of the Test of Infant Motor Performance (TIMP)" (Campbell et al., 1995) has been proclaimed the best paper published in the journal Physical Therapy in 1995. This paper is based on Rasch analysis of 174 administrations of a 27 item protocol. Test administration comprised observing both spontaneous and provoked actions of babies ranging in age from premature to 4 months old.
TIMP is designed to be used by therapists as part of their management of a baby's health. It is intended to signal developmental deviance at an early stage so that effective intervention can prevent serious impairment. Thus it is a "high stakes" test for those at risk, but it must be administered by therapists with close contact and personal emotional involvement with the babies. Consequently thorough rater training is essential. One component of this involves videotapes. Each rater viewed and rated 14 videotapes of babies of variety or ages, impairment levels and racial origins. The Facets program was use to verify that the raters were homogeneous and consistent in their ratings.
The paper presents a detailed investigation of the item hierarchy, fit statistics and indicators of test reliability. These confirmed that TIMP is an effective measuring instrument, but also identified areas for refinement.
Most interesting are the plots of baby development. These are the fruit of the careful work in measurement construction invested in the TIMP. Figure 1 (Paper Figure 5) shows motor performance development for normal children. Figure 2(Paper Figure 6) shows motor performance development for high-risk children. Trend lines have been drawn in on both plots. The plots show that high-risk babies start lower and grow slower. But the difference is slight at this early stage,indicating the need for careful measurement in order to detect it.
The paper also forms the basis for speculation about a pivotal date in motor development. Figure 3 is plotted from the Paper's Table 2, which reports average Motor Measures for low-risk babies at various post-conception ages. In Figure 3,the right-hand Y-axis together with the lower-plotted line suggests logarithmic growth in motor ability. When the same information is log-scaled and plotted against the left-hand Y-axis it forms a straight line. The rescaling is based on the logarithm of (post-conception days - 229). This hints that 230 days, i.e., 7½months, after conception is a pivotal point in foetal motor development. This connects with Lee's speculation (RMT 6:4 p. 245-246) that a pivotal date for reading ability is birth and for math ability is conception. Careful measurement has always provided the means by which science can make startling advances.
"This.. suggests some of the implications of measurement. A good theory can be promptly compromised or greatly enhanced through this process. Also, the way in which measurement alternatives are identified and selected, and measurement problems anticipated and resolved, influences the development, choice, and use of frameworks that guide the researcher in deciding what strategies and techniques are most appropriate to those frameworks. In affecting the validity of research results,the measurement process has repercussions for the ongoing revision and improvement of theory" (Blalock A.B., Blalock H.M. 1982. Introduction to Social Research. 2nd Edn. Englewood Cliffs NJ: Prentice-Hall. p. 37).
John M. Linacre
Campbell SK, Kolobe THA, Osten ET, Lenke M, Girolami GL. 1995. Construct Validity of the Test of Infant Motor Performance. Physical Therapy 75:7 p.585-596.
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Campbell S.K. et al. (1996) Year's best paper in Physical Therapy. Rasch Measurement Transactions 10:2 p. 489-490.
Year's best paper in Physical Therapy. Campbell S.K. et al. Rasch Measurement Transactions, 1996, 10:2 p. 489-490
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