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Consider the following graph and the 7th and 8th statements.

[![enter image description
here](https://i.stack.imgur.com/kFfdV.jpg)](https://i.stack.imgur.com/kFfdV.jpg)

For me, the 7th and 8th statements are ambiguous.

## 7th statement

  * If we consider the statement only by subtracting 13.2 from 18.9 which is 5.7 then the statement is true. 

  * But if we calculate the percentage of increment by (18.9-13.2)/13.2 = 0.43 then the statement is false.

## 8th statement

  * If we consider the statement only by comparing 2 consecutive years then the statement is true.

  * However, if comparison can be performed on any pairs then the statement will be false because the most decrements occur between 1965 and 2001.

# Questions

Do you think these 2 statements ambiguous? Or there are some conventions among
Japanese that I miss here.
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meaning
Conventions used to comprehend graphs, charts, etc
I think the ambiguity is taken away by two phrases in both statements:

>   * 1985年から2001年 **の間に**...5%以上増えた
>   * ...もっとも大きく下がっているのは、1975年から80年 **にかけて** である
>

The first statement indicates that what is being compared is only the
difference between _beginning_ percentage and _final_ percentage for the date
range given.

The second statement however, is comparing what happened "over a period of
time" and logically may require more complex calculation than simply finding
the difference between the beginning and end of the period in question.

There is no in-between data for this second statement in the graph though, so
in this context finding the difference should be enough to determine the
accuracy of the statement.
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### 7th statement

Yes, the 7th statement (" _n_ percent increase from _m_ percent") is ambiguous
(between `n+m` percent and `m*(100+n)/100` percent), and I believe a careful
writer should never make a sentence like this.

The literal interpretation is the latter, but in reality, people who are not
good at math often make a sentence like this. If I were forced to answer this
question, I would answer "○ (true)" assuming the questioner is having `18.9 -
13.2 = 5.7 > 5` in mind. (But luckily, the answer will be true anyway, because
`(18.9-13.2)/13.2 = 0.43` is a **43% increase** , which is larger than 5%
(=0.05).)

To avoid the ambiguity, you should use **ポイント** (の上昇/低下/etc) to refer to the
simple arithmetic difference of the two percentages. 「たばこを吸う女性の割合は5ポイント以上増えた」
always refers to `18.9 - 13.2 = 5.7 > 5`.

  * [何％ではなく何ポイント上昇などというのは何故](http://oshiete.goo.ne.jp/qa/697847.html)
  * [Percentage point](https://en.wikipedia.org/wiki/Percentage_point) (English Wikipedia)
  * [パーセント](https://ja.wikipedia.org/wiki/%E3%83%91%E3%83%BC%E3%82%BB%E3%83%B3%E3%83%88) (Japanese Wikipedia) 

> 「支持率が50%から10%増加して60%になった」などという表現は誤用である。50%から10%の増加であれば、 0.50 + (0.50×0.10) =
> 0.55 =
> 55%だからである。正しくは「支持率が50%から10パーセントポイント増加して60%になった」と表記する。なお、「パーセントポイント」は単に「ポイント」と言われることも多く、日本では「パーセントポイント」と言われることは稀である。

### 8th statement

I think you can safely assume that the questioner is focusing on the
increase/decrease happened in each 5-year section here. So you can calculate
the difference of each adjacent pair of numbers (ie, `86.7-81`, `81-76.3`,
`76.3-69.1`, ...) and get the 5-year section where the difference is the
largest.
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