Grand Blue – Deviation Value

Context: There was a mathematical term used in the manga that is only really used in Japan. This blog post is mainly to explain what it is. The line is located on the cover page of Chapter 37 (above the title). We used Love Quotient in the end instead of Deviation Value, but I think the concept is interesting still.

Deviation Value:

Deviation Value is a mathematical concept used in Japan, primarily by the education/school system. It follows the same statistical concepts of z-scores that we use in the western world, but has a slightly more specialized formula. There’s going to be a lot of math, so if you’re only interested in translation-related stuff skip to the end. TL;DR: Deviation Value is Z-score with mean 50 and standard deviation 10.

The formula is as follows:


Source: Wikipedia Japan

The formula we use in the rest of the world to calculate Z-score is

Standard Score Calculation

(taken from

Described literally, a Z-score is the number of standard deviations an individual value differs from the mean. For example, a Z-value of 0.66 would be described as “0.66 standard deviations to the right of the mean”. Z-values typically vary from -4 to 4, since 99% of values fall within this range. The score is used to identify where an individual value falls within a sample, or to find the interval where a certain percentage of the sample falls (for example, top 10%). These percentage values are generally found through consulting a z-score table such as this.

Image result for z-score table

As you see, this table only goes up to 3.49 since that covers most values already.

It appears that Deviation Value is essentially the same thing as a z-score, except standardized to be centered around the value 50, and one standard deviation = 10 DeviationValue. Essentially, to convert from Deviation Value to Z-score, we use the formula

Z-score = (DeviationValue-50)/10

I’m not entirely sure why the Japanese use this system. Maybe it’s easier to think with factors of tens in Japanese, rather than having decimal numbers.

Moving on to the translation, the phrase we had to translate was 恋愛偏差値25野郎どもの現代神話!. There are a lot of interesting things going on this phrase, mainly in word choice.


Literally means “love”, however it is being used as the “field/subject/population” in which these idiots fall 2.5 standard deviations below the average.


Converting a Deviation Value of 25 into Z-score:

Z-score = (25-50)/10 = -2.5 -> bottom 0.0062%

Localization would use z-score. Lit. translation would use deviation value. Liberal would maybe try using bottom 0.0062%.


This is kind of a generic insult/moniker. Due to the series, I think “idiots” is appropriate, although maybe a bit liberal.


It’s a bit clunky, but I want to keep the exact phrasing of “modern-day legend”. I like respecting the author’s word choice.

Putting it all together… I tend to pick and choose from different styles to get a line which sounds nice in my head.

A modern-day legend of idiots with a Z-score of -2.5 in love!

This is what I first came up with, although I’m a bit uncomfortable because of how the phrasing ‘in love’ works. This can be parsed as “A modern day legend of idiots with a Z-score of -2.5, now falling in love!”, when the actual meaning of the line is that these idiots are terrible at love. (The wording of love is awkward in general to be honest… ugh). This is when I learned that there was a T.V show called 恋愛偏差値, or “Love Quotient” in english. I don’t believe that the line is an actual reference to this show(since I believe it is a statistics joke), but we can borrow that phrasing since it isn’t half bad! (People can come read this long ass translation note if they care about the finer details).

“A modern day legends of idiots with a love quotient of 25”!

I really want to use Z-score since it adds to the theme of the chapter, but it’s a bit difficult to fit into a nice-sounding line in english.

Bonus: Measurement Error.

I wanted to go with Systematic Error, which is a more precise term for this kind of measurement error. Kenji describes it in the script as “the error that occurs when measuring values that are smaller than the gradient markings on the measurement device”. Our PR viewed this as a resolution error, while I view it from the point of view of “human error”. I believe the difference between analog and digital measuring devices is the removal of human measurement from the equation that makes the digital measurement more accurate. Both of these kinds of errors exist though, so it is essentially an argument about nothing in the end. In the end PR wanted measurement error since it makes more sense to the layman. I like Systematic Error a lot more since I believe it would lend to the tone of the chapter more, but it’s more or less the same.

Although short, this is one of the better chapters in my opinion.

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