Hypothetical case:

In a 2004 traffic study of a certain stretch of freeway, 75% of the people driving on freeways exceeded the speed limit. In 2005 traffic cameras were installed on freeways to photograph and ticket speeders. In 2006, along the same stretch of freeway, 50% of the people driving on freeways exceeded the speed limit.

Comparing 2004 and 2006, approximately how much of a reduction in speeders was there?

A) 25%
B) 33%
C) 50%
D) 75%

Depends on how you phrase your answer.

There was a decrease of 25%

There were 33% fewer speeders.

Also, in the question you used 'were' when you should have said 'was'.


eta: But yeah, this is a neat one, thanks for bringing it up.  It stymies a lot of people, even at high levels, because it's very difficult in this situation to communicate precisely what you mean.

Even more dramatic, I think, are cases where, say, 2% of x individuals are (+).  Later, 4% of individuals are (+).   There were 100% more, a 2% increase

Quoted: Depends on how you phrase your answer. There was a decrease of 25%

25% of what?

Quoted: There were 33% fewer speeders.

Yes, and there was also a decrease of 33% too.

IOW, the % of speeders decreased in 2006 by 33% of what it was in 2004.

% of speeders in 2006 = 33% * 75%

Quoted: Also, in the question you used 'were' when you should have said 'was'.

English weren't my strong subjects.

Yep, 33%.



Say theres 1,000,000 people driving.  75% of those are speeders.  750,000.


Then, the next year, 1,000,000 driving.  But 50% speeders.  500,000.

So 750k down to 500k is 33% reduction.

Quoted: Hypothetical case: In a 2004 traffic study of a certain stretch of freeway, 75% of the people driving on freeways exceeded the speed limit. In 2005 traffic cameras were installed on freeways to photograph and ticket speeders. In 2006, along the same stretch of freeway, 50% of the people driving on freeways exceeded the speed limit. Comparing 2004 and 2006, approximately how much of a reduction in speeders was there? A) 25% B) 33% C) 50% D) 75%

25% of all drivers ceased speeding.  33% of all speeders ceased speeding.

Quoted: Quoted: Hypothetical case: In a 2004 traffic study of a certain stretch of freeway, 75% of the people driving on freeways exceeded the speed limit. In 2005 traffic cameras were installed on freeways to photograph and ticket speeders. In 2006, along the same stretch of freeway, 50% of the people driving on freeways exceeded the speed limit. Comparing 2004 and 2006, approximately how much of a reduction in speeders was there? A) 25% B) 33% C) 50% D) 75% 25% of all drivers ceased speeding. That wasn't the question, but that's true. 33% of all speeders ceased speeding.That's correct also.