# Introducing myself

## DiscussãoUnique Library Thing Book Group

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### 1islandbooks

Hi,

Nice group, I've just joined.

I discovered this group about an hour and a half ago and I could add the ULTB tag to over 200 books from the 1700 books I currently entered into LT. (I'm not bragging, it's just fun.)

I'm curious what the Median/mean book obscurity is for other members of this group. Mine is 7/332.

All the best,

Martin

Nice group, I've just joined.

I discovered this group about an hour and a half ago and I could add the ULTB tag to over 200 books from the 1700 books I currently entered into LT. (I'm not bragging, it's just fun.)

I'm curious what the Median/mean book obscurity is for other members of this group. Mine is 7/332.

All the best,

Martin

### 2SaintSunniva

For what it's worth, the Median/Mean book obscurity of my library is 19/349 in a collection of about 3600. I had over 300 ultb's, but hadn't checked on them for a while. Now I'm under 300 - just deleted a bunch.

### 5misericordia

Welcome to the group!

The Obscurity measurement is...well obscure at best.

The best definition I could find is

"The number before the slash is the median obscurity of the books in your library, and the number after the slash is the mean. And the lower the numbers the more obscure your library is."

The test is to add or subtract a really popular book like Twilight or Harry potter and see what it does to your numbers.

Oh and 36:614 a very poor Obscurity rating...

The Obscurity measurement is...well obscure at best.

The best definition I could find is

"The number before the slash is the median obscurity of the books in your library, and the number after the slash is the mean. And the lower the numbers the more obscure your library is."

The test is to add or subtract a really popular book like Twilight or Harry potter and see what it does to your numbers.

Oh and 36:614 a very poor Obscurity rating...

### 6setnahkt

The way I understand it:

Median book obscurity:

Sort your library by number of members. Your median book obscurity is the number of books you share with the "middle" member. For example, if your library only has 3 books, and they are owned by 600, 60, and 6 members, your median book obscurity is 60.

Mean book obscurity:

The total books you share divided by the number of books you own. In the above example, the total shared books is 666 (600+60+6), your library is 3 books, thus your mean book obscurity is 222.

The difference between the median and mean is a measure of how "normal" (in the statistical sense) your library is. For example, if the hypothetical three book library had 60, 60, and 60 as the book-shared numbers, the median would be 60, so would the mean, and the library is "normal" If it were 6, 60 and 60000, the median is still 60 but the mean is now 20022 and the library is "skewed". Using the median diminshes the effect of very popular works; using the mean increases it.

Looking at it another way, let's say there's a bunch of people in my library and I pull a book off the shelf at random -

Median book obscurity:

Sort your library by number of members. Your median book obscurity is the number of books you share with the "middle" member. For example, if your library only has 3 books, and they are owned by 600, 60, and 6 members, your median book obscurity is 60.

Mean book obscurity:

The total books you share divided by the number of books you own. In the above example, the total shared books is 666 (600+60+6), your library is 3 books, thus your mean book obscurity is 222.

The difference between the median and mean is a measure of how "normal" (in the statistical sense) your library is. For example, if the hypothetical three book library had 60, 60, and 60 as the book-shared numbers, the median would be 60, so would the mean, and the library is "normal" If it were 6, 60 and 60000, the median is still 60 but the mean is now 20022 and the library is "skewed". Using the median diminshes the effect of very popular works; using the mean increases it.

Looking at it another way, let's say there's a bunch of people in my library and I pull a book off the shelf at random -

*1990 Society of Vertebrate Paleontology Upper Paleozoic of Eastern Kansas Excursion Guidebook*, say. With my library's low median obscurity number, the chances that somebody else in the room has read that book are very small. However, since I have a relatively high mean obscurity number, the chance that there is at least one book in the library -*Great Expectations*, say - that we can all talk about is relatively high.### 7sarahemmm

You prompted me to check: I'm currently at 138/743, though another 3 are no longer ultbs.

### 8misericordia

6> Thanks for the explanation. "1990 Society of Vertebrate Paleontology Upper Paleozoic of Eastern Kansas Excursion Guidebook" ooooh, I bet that's a page turner ;)