In the end of פרק ו, Koheles is in search of the worthy man, free of sin. פסוק כ"ח says: "אדם אחד מאלף מצאתי ואשה בכל אלה לא מצאתי." I have found one man in a thousand. And a women in all of these I have not found. I'm not quite sure how to understand this and right now, I'm not going to try. But R' Chaim Kanievsky has a startling ha'ara on this pasuk which vastly changes how we approach it mathematically.
If we were to look at this pasuk statistically, one would say that the ratio of worthy men is 1:1000 and of worthy women is 0. Not so, says R' Chaim. In no place do we ever find the word "אדם" referring only to males. It refers to Man as a species. Therefore, we must view the 1000 as being a mixture of men and women, presumably an even mixture of 500 and 500. Koheles therefore tells us that one in a thousand human beings are worthy. And within this thousandth, he found none to be women. Although this doesn't change the state of the women, it does change the ratio of worthiness for the men. Instead of a 1:1000 worthiness ratio, according to R' Chaim Kanievsky's interpretation of the pasuk, it is 1:500.