Monday, November 12, 2007

Now for some historically poor examples of valid and reliable measurements.

What’s a “foot.” (Measurement)
What’s a cubit? (When I think about cubit I often think about the old Bill Cosby monologue <http://msxml.excite.com/info.xcite/clickit/search?r_aid=7AFE09E17BF54135B9C52579F61E71C0&r_eop=1&r_sacop=3&r_spf=0&r_cop=main-title&r_snpp=2&r_spp=1&qqn=5V%40ex3Z%40&r_coid=239138&rawto=http://www.jr.co.il/humor/noah4.txt>) If you ever get a chance to hear it, it's worth it. Bill Cosby is one of the premiere comedians of my life time. This bring out another important point about plan writing and measurement and keeping things valid and reliable. My life time probably covers a lot more time that yours. I've read some reports where people have used generational slang. Keep it professional. Remember that other professionals will be reading what you write. Don’t use slang, "expressions" or acronyms.

Some additional examples:
Many surveys are reliable yet not valid; they do not accurately report what they claim to report.
Some assessments are not accurate across cultures or individual situations. For example some IQ tests are not valid across cultures.
Another example, a standard eye test is not valid for a non reader. (I remember living and working in a group home when I was younger. I took a non reader to an eye doctor for his annual exam. The doctor took the man and gave him a test and returned and told me he was legally blind. He wasn't legally blind. The Optometrist had showed him a letter and asked him what it was and he would just simply say: "I duno!" and shake his head. Knowing that this person had good vision I spoke with the doctor who tried a different type of test where they many only had to point. His vision was 20/20.

Some additional threats to Validity are: Multiple Variables; Something else happened or is happening at the same time. Maturation: The participant grows into it or out if it and would have without the intervention (this is one of those "other" variables" mentioned earlier); Observer Bias, We see what we wantor expect to see.

To continue with this information click here: Goals

2 comments:

CR Petersen said...

Original a “foot” was the length of the kings foot. How reliable or valid is that? A cubit is the length from the elbow to the end of the middle finger. Obviously this is not a reliable instrument, even for the same person if you consider maturation from a child to an adult.

CR Petersen said...

The same person may measure a cubit over and over again and get the same result, which makes it partially reliable; however, that same person over time (maturation) may not get the same result. Different people may also get different results. It is still a cubit though and so for a cubit, it is a valid and accurate measurement; however as a measurement tool and over time and across different people, it is neither particularly reliable, valid or accurate.