#### Comment Preferences

• ##### Thanks for showing math!(2+ / 0-)
Recommended by:
neroden, plf515

All too often statistics is presented ex nihilo, as the voice of god.  Thanks for showing the guts of the calculation - I was able to reach waaaaay back to middle school exploration of statistics and, with a little googling, make sense of it.  Great!

• ##### You're welcome!(2+ / 0-)
Recommended by:
Del C, ManfromMiddletown

ask any questions.... I am sure others have similar questions.

• ##### Not so much a question as a technical comment.(1+ / 0-)
Recommended by:
plf515

beware the ecological fallacy.

You're extrapolating the characterestics of individual voters from aggegrate data.  In this case you're using measures of central tendency of the whole, (i.e. means, medians, maybe even modes?) to say something about the parts.  Equally important are measures of dispersion (i.e. standard deviation) that tell us about the distribution of cases within the aggregate.

A commonsense illustration.

I have two tubs of water to put my feet in.  The two aren't the same temperature, but I know that the mean for the 2 is 100 degrees so no big problem, right?

Potentially very wrong.  Measures of dispersion matter.  If one tub is 95 degrees and the other is 105, no big deal.  But if one tub is 40 degrees and the other is 160 degrees, the mean remains 100 degrees.  Obviously, the latter case is substantially different from the former.  Drawing a conclusion about the parts from the whole in the former case where measures of dispersion would be low is much less prone to ecological fallacy than the latter case.

• ##### I explicitly warned against the(1+ / 0-)
Recommended by:
ManfromMiddletown

ecological fallacy in the diary.

You're quite right that it's a problem, but this diary is about districts, not individuals.

• ##### I expected that you knew(1+ / 0-)
Recommended by:
plf515

this, however I think that it's something that needs to be made explicit when dealing with persons who don't have the statistics background to take this as a given.

• ##### You're right(0+ / 0-)

it's one of the fallacies that is easy to fall into, and hard to see the logic of.

Subscribe or Donate to support Daily Kos.

• Recommended (128)
• Community (59)
• 2016 (50)
• Environment (39)
• Elections (37)
• Media (34)
• Republicans (32)
• Hillary Clinton (31)
• Law (29)
• Jeb Bush (29)
• Culture (27)
• Iraq (27)
• Barack Obama (26)
• Climate Change (25)
• Trans-Pacific Partnership (25)
• Civil Rights (24)
• Labor (20)
• Economy (20)
• LGBT (16)
• Congress (15)