why don't some tables I'm studying in a column add up to 100%? Example: N=338, but responses to questions asked in survey I'm studying equal of 24.3, 9.8, 43.8, DON'T add up to 100%. I'm assuming that some people surveyed out of the 338 didn't bother responding, but is there another problem related to proportion or ratio being used, but improperly labeled on graph?. Note at bottom of table says: "number in parenthesis are numbers of cases" and 338 was in parentheses. I'm lost.


When reading published results from surveys you need to be very careful. It is common for researchers and the media to ignore nonresponses. In the table that you have it seems that there should be a "nonresponse" row with 22.1% in it. At least in this table you can calculate the percentage of nonresponses.

You are correct to be concerned about proportions and percentages as you need always ask "the proportion or percentage of WHAT?". In many cases the published results of a survey will say something like "21% supported option A". In this case you have to look carefully to see if this is 21% of the people asked or 21% of the people who answered.

I hope this helps,
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