Hi,

I have downloaded ADHD data set, and I am planning to use it in my research
course, but I have many questions. Could you please help me to have better
understanding? Here are my questions :( some of these questions may look silly,
but it’s very important for me to understand everything to describe this data
to my professor)

1. For the age... 13.58 means 13 years and 58 days?

No, it would mean 13 years and 365.2425*.58 days (or 13 years and 212 days).

2. -999 mean missing value?

yes

3. What is the meaning of the values for the variable Handedness that
belong to NYU? Handedness has only three values 0 Left, 1 Right, and 2Ambidextrous.
But their values contain different numbers like 0.67?

For NYU handedness was assessed with the Edinburgh Handedness Inventory. The scores are represented in the phenotypic file. Numbers > 0 mean right handed. The higher the number the stronger the preference.

4.  How the variable “DX” was
measured? Is it based on medical examination “fMRI”?

The diagnosis was for most sites determined by a clinical interview combined with behavioral questionnaires.

5. What is Full IQ? and which IQ score we use ?

For most sites IQ was determined with one of the Wechsler IQ scales. See here: http://en.wikipedia.org/wiki/Wechsler_Adult_Intelligence_Scale

Full IQ would be the IQ based on the scores of all subtests. However, instead of administering the full scale it is often abbreviated to a couple of subtests. In that case Full IQ would be an estimation (there are formulas for that).

6. What are QC_Rest and QC_Anatomical?

QC_Rest and QC_Anatomical are non-binding quality control calls. Someone at the NYU lab went through all images and assessed their quality. This resulted in a 1 if the image passed, 0 if the quality was questionable. However, like I said, these are non-binding calls. They are indicative only, you are entirely free to make your own quality assessments of the data.

I appreciate your cooperation,

Thanks,

Maryam