A good data definition provides ALL the characteristics forms (questionnaires, CRFs) and associated variables. What is needed is good old "TLV".

	Stands For..	Overview
T	Type of Variable	The most common types are dates, number, coded variables (e.g., 0 = No, 1 = Yes; Tell us if more than one option can be selected).
L	Layout and Logic	Indicate the look and feel of the variable, and when it should be displayed (e.g., only show if subject is a male).
V	Validation	Indicate the rules that govern the acceptable variable values (acceptable range, units)

T - Type of Variable

Use A Spreadsheet

Document your data definition using the spreadsheet here.

Mark It UP

If sending us forms (CRFs), mark up the form with the data definition.

L - Layout and Logic

The standard layout a is one row per variable layout (see here) which is standard practice and always used if possible.

The standard loo

Attribute	What’s Needed
History	Is the form (or similar form) in another StudyTRAX project?
Formatting and Layout	Will subjects enter the data? (i.e, need multi-device format)
	Does the format / layout matter? (easiest/simplest electronic user-experience)
	Describe any special formatting
Skip Patterns	When is the variable/form either shown / hidden?

Form	Skip logic / condition
Pregnancy Test	Hide form for males
Demographic Data	Show text box if ‘other’ is selected for Race

Attribute	What’s Needed	Our Default
Variable Name	Descriptive Name
	Unique code (no spaces/special characters [underscore ok])
Variable Type	Numeric – What is the range (min / max)? Units?	No range, no unit
	Calculation - How calculated? What if missing some values?	All values required for a calculation
	Text - How many characters needed? Text variables require a limit (can range from 1 to 255 characters) Memo variables do not have a limit	Unlimited for questions like Describe, Comments
	Date – What is acceptable range?	Any valid date can be entered
	Document – How many files and how large?
	Coded list (e.g., 0 = Male…) · What are the values and labels for all options? - do you want values displayed for data entry? · Can more than one option be selected?	0=No, 1=Yes Other lists would start with 0 and increment by 1 Values are not displayed Only one option can be selected
Definition	Export – Can values be exported in dataset?	Exportable
	Missing Values – Will values be assigned as “Missing” (e.g., Missing = -9)?	No missing value definition set up if not specified
Required	Must a value be entered?	Yes

Time	-10d	Day 0	Day 7	Month 3	Month 6	Protocol Deviation	Adverse Event
Windows	±10dys		±1day	±2wks	±1mth	N/A	N/A
Visit	Screening	Baseline	Visit 1	Visit 2	Visit 3	*Protocol Deviation	*AE
Visit Overview	X	X	X	X	X
Study Eligibility	X
Physical Exam	X	X	X	X	X		X
Demographic Data	X
Complete Blood Count (CBC)	X		X	X	X
Electrocardiogram (ECG)	X	X			X
Pregnancy Test	X	X			X
Tuberculosis Test	X
Vital Signs	X	X	X	X	X		X
Adverse Event (AE) form							X
Protocol Deviation						X

X = forms required to be filled out for visit

*Event created and forms completed as needed