Swimming in Statistics

I saw a YouTube video last night in which the presenter gave some statistics about blindness and people who are blind.   It was a good video, but the statistics listed didn't match or were even close to some of the information I've heard before, so today I set aside some time to do research using the World Wide Web to find out if I was out of date or just plain wrong.

I am frequently reminded of a quote by Robert Heinlein from, "Assignment in Eternity" about facts.   It's a long passage so I cut out the bit in the middle.   The reason I remember this particular passage which is a fairly negative evaluation of humans, is to remind me not to fall prey to assuming I know something as fact, simply from hearing someone say something is so.

If the average man thinks at all, he does silly things like generalizing from a single datum. He uses one-valued logics. If he is exceptionally bright, he may use two-valued, either-or, logic to arrive at his wrong answers. ... .Far from aspiring to higher reasoning, he is not even aware that higher reasoning exists. He classes his own mental process as being of the same sort as the genius of an Einstein. Man is not a rational animal; he is a rationalizing animal.

This is why today I went to do some research on blindness and vision impairment so I could have confidence I knew what I was talking about.   I thought it would be easier than it is however and after lots of searches, articles read, charts, and graphs reviewed, I still don't have the answers I want to know for myself personally and to write here with reasonable confidence.  

Here are some of the questions and definitions I discovered I needed to know in order to find the particular statistics I was looking for:

• What does it mean to be blind?   Is it total blindness or the inability to be able to have vision corrected with lenses so.  How blind do you have to be to be blind?  One site stated, "we encourage people to consider themselves blind if their sight is bad enough—even with corrective lenses—that they must have alternative methods to engage in any activity that people with normal vision would do so using their eyes."   
• What does it mean to be "legally blind?"   This question was easier.  If you have 20/200 or worse in your best eye with best corrective lenses you are considered legally blind. 
• What does it mean to be "visually impaired?"   In this case, if your best-corrected vision is 2040 or worse, you are considered visually impaired. 
• Some statistics referred to children with "vision difficulty" which I haven't found a consistent definition for. 
• Data is collected from many agencies and organizations (which is great) but the data doesn't always agree.  They all state confidence intervals and sample sizes, but the data collected don't sync up.  For instance, one reports data on populations aged fifty and older while another uses forty and older.  Some studies class children as eighteen and under while others use twenty-one and under. 
• Is blindness or vision impairment defined by what you can see currently, or what your best vision would be?  In many developing countries some students are treated as blind simply because they have no funds to get corrective lenses while would otherwise allow them to see normally or near normal.
• I found some data for the United States but there is also information on North America that seems strikingly different.
• I found one site which has maps and data from a comprehensive database of eye studies.  I thought that synthesized data would be what I was looking for but the summary information was less specific than what I was looking for.  \\

The thing I read, again and again, that could factor into the statistical results was that data was based on self-reporting of individuals.  Numbers might vary significantly.  Or they might not.   When I was in college as a Freshma I took a course in statistics and I learned about confidence intervals.   It seemed like magic at the time when I first figured them out but once I understood it, I thought it was about the coolest thing and I've never forgotten it.   So even though there may be a lack of self-reporting, the variance isn't huge. 

At the end of my research today, I have lots of notes with all sorts of numbers, each of them interesting individually but together it's not the overall statistics I'm looking for.   So I have more work to do.   To be continued...

The Big Boy Update:  For some reason, my son is really has been wearing long pants and a sweatshirt lately.   It's not that cold inside, in fact the second floor is even having a hard time keeping pace with the close to one-hundred degree weather we're having here.   He seems happy in his warm weather gear though.  

The Tiny Girl Chronicles:  My daughter had music therapy today outside to provide for extra social distancing with Chelsea.   Chelsea had her guitar on the grass in the back yard when I looked out to see my daughter straggled on the top of the A-frame of the swing set, reaching over and down to adjust a swing.  I called out from the deck, "is that something you all have been doing?" with some alarm in my voice.  Apparently it is something they've been doing and they've been careful about it, my daughter told me.   After she got the swing to the height she wanted, music therapy in the outdoors commenced without incident.