Table 1.

Attributes of measurement tools.

Attribute	Definition	Questions when selecting a measurement tool for fine motor skills in movement disorders involving tremor
(A) ATTRIBUTES OF ALL MEASUREMENT TOOLS
Conceptual and measurement model	Rationale for and description of concepts and populations a measure is intended to assess, and in what populations	Does the tool evaluate fine motor skills per se? Was it developed for a particular patient population? Does it measure a broad construct, within which fine motor skills are merely a component? Does it purport to represent the progression of a specific disease? Or does it purport to represent impairment or disability more generally?
Scaling assumptions	Degree to which it is legitimate to sum scale or subscale scores, implying the sum reflects a common underlying construct	Are the items in the scale or subscale related to a common underlying construct relevant to fine motor skills?
Validity	Degree to which instrument tools measures what it purports to measure, including content, construct, and criterion validity	Do the tool’s scores have known relationships to any other measures of fine motor skills?
Reliability	Degree to which measure is free from random error, including test-retest and inter-rater reproducibility	Are scores consistent across raters and on separate occasions when patient status is thought to have remained stable?
Responsiveness	Ability to detect change over time that is clinically relevant	Does the tool have sufficient responsiveness to indicate when a clinically meaningful change in fine motor skills has occurred? Is the minimal clinically important difference known for the population being investigated?
Targeting	Extent to which items of a tool are acceptable for the population under investigation	Is the tool targeted to a specific movement disorder involving tremor or is it generic, potentially applicable to people of various conditions? Also, are the scores from subjects with tremor likely to cluster near the bottom (floor) or top (ceiling) of the possible range of scores on the measure? See also scope of hand function, below
Data completeness/quality	Degree to which all items of a tool can be obtained in each individual being evaluated	Is there a risk of missing data when the tool is used in subjects with movement disorders involving tremor?
Interpretability	Degree to which one can assign meaning to a tool’s quantitative scores	Is the relationship between measurement tool scores and the continuum of the construct being measured linear? Are there established norms for age and/or gender in healthy subjects, movement disorders involving tremor, or other diseases?
Burden: respondent and administrative	Time, effort, cost, personnel, or other demands required to complete the tool	Is it uncomfortable, frustrating, or embarrassing for subjects to answer the questions or do the tasks? What is the cost and portability of the instrument? Are there ongoing costs? How much experience is required by the evaluator to obtain valid and reliable scores in the population of interest?
(B) ATTRIBUTES OF TOOLS TO MEASURE HAND FUNCTION
Scope of hand function	Extent to which tasks or items adequately capture the construct of fine motor skills	Are the conceptual model, scaling assumptions, and targeting of the tool appropriate for the selected aspect of hand movement function? Is the task (or set of tasks) appropriately comprehensive with respect to hand dexterity for the population in whom one intends to use the tool?
Handedness and bilateral tasks	Extent to which each hand is evaluated separately, and bilateral hand tasks are also evaluated	Because tremor can affect right and left hands differently, does the tool adequately capture each hand’s movement ability? If capturing natural function is important to the research or clinical question, does the tool include tasks that are normally done with two hands?
Relationship to learning or practice	Extent to which the performance of tasks or items is influenced by whether they are familiar and well-practiced	Are the tasks well-practiced for one hand, both hands, or neither? Have people learned compensatory strategies to perform tasks more quickly or smoothly? Is the familiarity and/or extent of compensation likely different between people?