|WikiProject Statistics||(Rated Start-class, High-importance)|
Ambiguity in 'twice as much'
someone please indicate the meaning of the 1st paragraph hypothesis... if population never changed, let's say 100 people. in the 80's 40% was smoking, in the 90's 30%. that's a reduction of 10 people. so, the change of 10 from 100, is 10%... where does the 25% cames from? — Preceding unsigned comment added by 184.108.40.206 (talk) 07:45, 3 December 2011 (UTC)
- 10 people who quit is 25% of 40 people who smoked. Abolen (talk) 20:01, 3 December 2011 (UTC)
- Still "assuming the same total population in both years" is wrong. That only needs to be true if the 25% should also reflect on the change of the absolute number of people who. A reduction from 40% to 30% is a 25% decrease, no matter how the population changed. The whole reason of using % is to become independent of the absolute numbers. And 30%/40%=0.75=75% and that is always true. Therefore, I will remove the false statement. --220.127.116.11 (talk) 12:36, 21 December 2011 (UTC)
I disagree with this statement in the article: "Statements such as "between 1980 and 1990, the smoking rate decreased twice as much as the lung cancer rate" are ambiguous: it is not clear whether percentages or percentage points are being compared."
I don't see how it is ambiguous. By saying "the smoking rate decreased twice as much as the lung cancer rate" the speaker would merely be saying that the decrease of one was twice the value of the other. I see how a statement could be incorrect when a speaker misuses the term "percent" but that term is not mentioned in this sentence. When no specific unit is mention it is convention to assume the author is referring to absolute value. Therefore, one must also assume that if one were to nominate a unit of measurement to be applied to the value referred to as decreasing, then one would also have to apply the same unit of measurement to the the value with which it is being compared. After all, you don't very often hear a beef farmer say "my herd of cows has decreased by twice as many chickens as last year" do you now?
- Suppose smoking rate decreases from fraction 0.2 to 0.1 of the population, while lung cancer rate decreases from 0.01 to 0.005 of the population per year. Then the decreases here are either
- a fall in both cases by a factor 0.5
- a reduction of the fraction affected by 0.1 of the population in the first case, or 0.005 in the second case.
- So here the "descrease" is either the same or different by a factor of 200 depending on whether change is measured multiplicatively or additively. It might be better to describle this avoiding percentages, but the article is about "percentage points". Melcombe (talk) 18:28, 6 January 2012 (UTC)
- Some of this is discussed further in Relative change and difference, and perhaps all of the "measuring change" stuff could be moved/dealt with there. That article has a few external links/references, but I don't know if they are relevant to this particular point. Melcombe (talk) 13:43, 30 January 2012 (UTC)
- It's pp. But is there supposed to be a space before it? — Preceding unsigned comment added by 18.104.22.168 (talk) 22:45, 31 July 2012 (UTC)
e.g. going from 1% to 9% is an 8 percentage point increase. Who point the citation needed tag in the opening line? Why? Why would a citation be needed for such an obvious fact? Is someone trying to suggest that they believe the increase is actually 8 percent?--XANIA - ЗAНИAWikipedia talk | Wikibooks talk 23:21, 15 December 2014 (UTC)