understanding INR range and variation using statistics

I've been working with managing my INR for some 14 years now (so, not really long), but as well I've helped a few others along the path of being able to self manage. This has been not only helpful for them, but a great learning experience for me too. One of the things I've had to do is teach an understanding of how to use basic statistics to help understand things. Things like the data we have about our INR. Lets look at this set of data, remember, these are daily measurements:

This person was just starting their warfarin therapy and we were working out the optimal dose required for them. We had to make some adjustments but we ended up on 9.5mg daily. You can see from the above that there are some ups and downs;

• for the most part we've been at or above 2
• we've kept times above 3 small (being even as high as 4 isn't really significant)

What we don't really know is "how well we meet the ideal target of 2.5" which was set by the doctors. We could average all those numbers and then know that. In this case the average was 2.57, so that's great! But if we ask "is this variation large" we don't really know. This is where some statistics tools comes in handy.

Statistics is something most of us use but try hard to ignore (probably) because of the trauma of high school maths classes; but we shouldn't because its really helpful. One doesn't need to know how to do the hard work to get the benefits because spread sheets have all this functionality built in; all you have to do is have the data in a column and use a formula to get it all worked out for you; write in =AVERAGE(E20:E130) and there it is.

I'm pretty sure most people are comfortable with average, but alone, average isn't helpful, you need its good mate the Standard Deviation. Lets go with an example: You know that the average height of 16 year old boys is 173.5cm. You have a boy from a class who's 185cm. So the question is "is he very tall or not really unexpectedly so"?

Intuitively we know that the answer is no, because we have experience with children. But if we also find out that the standard deviation is 7.4cm we know that anything between 166.1cm and 180.9cm is a totally expectable result. We know this because that is what Standard Deviation (SD) is designed to measure. Below is a curve which is called a "Normal Distribution", people who have been working in statistics for years know this curve well.

the Normal Curve

It shows us that 68.2% of people (in this case, but its also more generally "of measurements") will fit between -1 SD  and +1 SD (we use the lower case for Greek symbol sigma σ to represent SD which you'll see on the bottom axis of that graph of the Normal Curve).

So just like we know that most boys age 16 are between 166.1cm and 180.9cm we can use the SD to work out how much variation that person has from "the population". The SD for the data in that bar chart above is 0.41, which means that any variation we see where the INR is between 2.16 and 2.98 is entirely normal for this person. Note: we don't know about you because we don't have your data.

Next, looking at this we can see that quite a portion (about a quarter of all measurements) fall within 2 SD either side of the average (or μ) which means INR readings of 1.75 through to 3.39 are to be expected, but just not often. Also 1.34 through to 3.8 may come up (however rarely) and this would be statistically rare, but not impossible.

So how does this help us manage our INR?

It helps to know that if your regularly and reliably taking your regular dose and if you're regularly seeing your INR within 1SD of the average then you shouldn't really make any changes in your dose. Keep your dose consistent and you can then rely on the statistics to understand what is normal for you.

Looking back at the graph of INR we also see something else ... from measurement to measurement we typically don't see that much change. Sure there are a couple where "day to day" we saw substantial on the 1st of August where INR fell from 3.3, through 2.7 (next day) down to 2.3. This was the result of some changes; dose was dropped to 8.5 and it fell fairly quickly but as you see didn't drop below 2.1. The INR then ranged back towards the average within a week.

The approach we should have taken was "keep a steady hand on the tiller" combined with waiting for a few more readings. However ...

As a good (budding) statistician, if you do see a reading which is outside of the 1SD range and you know that nothing has changed (no new foods, no binging on grapefruit, no binging on greens) then you should expect it to gradually change back towards the average. Unless something has changed and you don't know it. If it stays higher then you know "something has changed" and investigation is warranted into what.

So, please do make friends with  both average and SD, incorporate that into your spreadsheet as well as using regular weekly measurements. Occasional mid week samples "just to know" are also often helpful, but as you can see from both the historical experience behind Average and SD, combined with regular dose and weekly readings you can be in INR range in the high 80% of the time.

To get into the 90's you just need a few more strategies ... but that's for another post.

Best Wishes

The Case evolution of early Seiko Divers

Now, this is undertaken with "homage" watches, but I've seen quite an amount of comparisons between the "homage" and the original to be satisfied that they are pretty close to the original. Indeed from what I've seen so close that even experts are satisfied and are frustrated that "Seiko didn't do this"

So, the order of release dates of these watches is this

1. 62MAS
2. 6105-8000
3. 6105-8101

What I'm wanting to do here is show what I've observed in the design evolution of the cases of these watches, which I think actually started with the 62MAS and then jumped over to the 6105-8000 case where it then morphed along into the divers case which ended up being refined into the SKX series.

So these watches are (usually if not always) seen by budding enthusiasts from a top down or slightly off angle top down. They are seldom handled, but instead seen like this:

62MAS (Seestern)

6105-8000 (Rdunae)

6105-8110 (Addiesdive)

My view is that this presentation hides what's happened. This is exacerbated by most people only looking at YouTube  and combined with the relative naivety of what amounts to a large fresh watch enthusiast audience (coming into watches post-COVID). 

First off, I want to remind readers that none of these in the Original Seiko had a screw-down crown. The 8xxx cases had a sort of locking crown and the MAS was just relying on its o-rings to seal. This point is not insignificant in watches that will need

1. reasonably frequent time setting (because they aren't quartz and so it was likely to have worse accuracy than 30 seconds per day (that's around 3.5 minutes per week)
2. date needs to be reset about 6 times per year.

This is important (as I've mentioned in other posts) because once you damage the threads in the tube within the body (not the crown which screws into that body) your watch is no longer waterproof and the crown sticks up higher waiting to get whacked probably bending the stem (and then the watch is finally junk).

Depending on if you're a person after a daily driver "tool watch" or a KingWang follower who is the tool for the "tool watch" this may or may not matter to you.

So lets look at what I find interesting; lets line these three up...

It looks to me that the 'machining style' of the case follows an unexpected pathway. Starting from a billet of metal, machining (at first) a slim and stylish (following the fashion cues of the past but morphing them) to make the iconic 8000 case of the 6105-8000 "Slim Case" from basically the same style of case scalloping out (carving out) that the 62MAS already started. Meanwhile "The Willard is basically flat on the bottom. The Willard is just a big fat blob of metal. In contrast the 8000 is a more sophisticated turtle shell shape.

Shaping, sculpting and polishing is beautiful and as you can imagine results in a rather significant weight reduction.

Returning to the MAS and the 8000, I've overlaid the MAS onto the 6105-8000 to show how much steel is cut away from the sides of that billet (making the MAS a more refined looking case) but remains present on the sides of the 8000 case. The 8110 remains a blob with the caseback actually sunk under the level of the case (gunk collection if you ask me).

 Indeed, look at the  tips of the lugs on the cases for a familiar line.

which interestingly didn't carry over to the 8110 case, which is basically a raw blob of metal and so to me, not properly a "Turtle Shell" case, which the 8000 case was.

So lets look from the face side.

This shaving off of metal (or leaving it there instead) results in a watch which is bigger and chunkier and I suspect may have been a way to use existing machining setups while allowing a move of the crown down to the (soon to be iconic) 4O'Clock position.

Now, overlaying the 63MAS outline over the 8000 we can again see that amount of extra metal and the crown position.

The astute will notice that the dial size is actually the same and that the gap in the case for the strap is 19mm on the Rdunae while the Seestern has "modernised" to allow 20mm lugs. Personally I think that was a bit of a wise step (despite what wangers may whinge about on line) because it opens up a vast array of straps (and frankly the Rdunae is shipped with a 20mm strap anyway and its just shoehorned in there).

You can see the (smallish) amount of case shaved "off from the lugs and case" of the 62MAS it is enough to account for the weight differences found here (link) of 66g vs 72g (or the 8000 being about 10% heavier). 

This of course alters the wearability of the watch for daily use compared to the later 6105-8000 (but the Willard at 94g pushes it further). Because I didn't get long with my 8000 (see here), I perhaps need to get another one to test this out, but both of these are very wearable daily divers, more than I can say for my personal experience of the Willard.

Anyway, to me these three watches are "iconic" for different reasons. I believe that the 6105-8000 would have fallen further into obscurity if not for Apocalypse Now and the success of the subsequent 8110 case series. I mean with The Willard its Win Win for Seiko, less machining and if the clients don't care about weight  then perfect (and to be honest, back in those days "Dive Watches weren't common nor were they worn all the time by owners.

Anyway, that's pretty much all I wanted to say here.

Enjoy your day 

Seestern 62MAS thoughts (and review?)

I think highly of this watch not least because of the Seiko heritage that it is paying tribute to, but because it is a very affordable, very well made watch that I can wear as a daily use watch. So this is written with something like 3 weeks of using it as an exclusive daily wear.

So I intend this to be a gloves off "nobody pays  me to write" assessment of this watch.

Bottom line

Seestern have enabled enthusiasts of the 62MAS to have access to a modern version of the watch which is much closer to the original than Seiko's reissues. It does so in a way that modernises critical things (like the movement, 20mm lug width, sapphire crystal) and enables us to have affordable reliable access to a piece of history. Perfect, well except for the high polished bezel and, well the larger size of the bezel being a distraction from the watch's proportions. This is more evident with both watches in hand than even this photograph:

That aside it is indeed a good match for the MAS. Having had both in my hand at the same time I can say that I prefer the bezel and crystal of the Seiko MAS by a mile (and its not subtle).

I like the Seestern a lot but I'm probably going to go back to my Seiko SRPE as my daily wear because of the things I've discovered along the way which I'll discuss here. I may bring it out more in Summer. Unlike my Addiesdives Willard however I'm not going to be selling this watch (I have a small collection with a simple rule of: one in = one out.

Discussion

Briefly the 62MAS marks Seiko's first foray into making a watch aimed at professional and serious amateur divers. I recommend that if you haven't, you look over at my earlier blog post here, which at the very least which serves as both a good introduction to my initial thoughts. There I also give the specs and a link to Fratello Watches post on the Seiko 62MAS which I will again source a portion of an image. 

The dial and the importance of the dial on a diver as being highly legible in all (and adverse) conditions. Key to reading a watch is orienting the dial so that not only is the 12 O'Clock clear but making the quarters of the dial immediately recognisable increases the accuracy of knowing where the hands point to by reducing the time to be clear about is it on the 9 or on the 10

Seiko knew that and made the markers on these positions reasonably visibly different. This is my first beef with the Seestern where they aren't. Actually as an aside my second beef with the Seestern is the visibly bigger bezel dial ring and it being that shitty shiny "make my watch look like a plastic toy" high polish ceramic. Most of the time it doesn't look black... Compare the thickness here where the font struggles to fit into the older one ... The extra thickness makes the bezel dial so much more 'present' on the watch.

But has plenty of room on the newer one ...

Anyway, back to the markers, keep in mind this magnification makes it easier to see the marker differences, compared with on your wrist, perhaps at night and if you're older than 40, perhaps without your glasses (which you only need as yet for reading small print).

This is most pronounced in the night time when the effect of dim light and 'bloom' of the lume conspires to make the 12 (and perhaps the lumed pip on the bezel if you have it kept up at 12).

The second hand lume is barely visible at all (although it is equally bright) because it sits atop the marker. So you can see that, if you're one of these options (over 40 need glasses) this is a small setback for this Homage over the original (and Seiko's reimagining isn't much better anyway). 

While Seestern tries to follow the same ideas of the Seiko

• tapering the lume ever so slightly towards the inner dial
• making them smaller than the quarter markers 

the taper is far too subtle and the ratio of length to width is also far too subtle. Forgive the colour temperature differences, that's down to lighting on my photograph.

Lets look at them all in better (bigger) detail

so at significant magnification the differences are clearer ... handy for the myopic who aren't wearing their glasses ... but not so much in a dive or dim lit situation.

Its important to remember that this is of course a very early Dive Watch, and Seiko was still learning the best design language for Divers watches. To  me this reached peak form in the 7000 series (like the SKX007) where dials and hands evolved to produce what to me is the pinnacle of diver dials. I don't have one of those, but I do have my SRPE which is very close visually to that series. A picture from my above mentioned earlier blog post shows that layout advantage clearly.

Almost instantly you can see the design cues guiding your eye to the hand positions clearly; markers are somehow less cluttered, quarters are distinguished from the others resulting in less time is needed to recognise the time) and so a quick glance is all that's needed. In terms of design language, the later watch has evolved into a clear 12, dashes on the quarters and  dots between them. So at a glance you can see is the hand next to a Dash, between two Dots or between Dash Dot / Dot Dash.

While the hands of the Seestern (which are pretty faithful to the Seiko 62MAS so important here) also make night time recognition harder because the lume on the hour hand is nearly the same width as the lumed markers and the minute hand is barely distinguishable from it (further compounding quick recognition legibility).

So despite being almost exactly the same size of face the MAS, the Seestern ends up looking cluttered and cramped while the more modern dial looks open and clear. 

For me this lack of legibility is a detraction, I wish they'd striven to make the small changes err towards being clearer (instead of less clear).

I like that that bezel on the Seestern is proud of the watch case; both in height and diameter. This makes it easy to grip and turn (as its intended to be); however this has an implication for wearing and long sleeves where it catches a lot.

Wearing the MAS

As I mentioned in the other post watch thickness is almost identical, with only the crystal protruding a bit more to make the watches differ in thickness. So the grip style on the bezel, and the fact that it stands a little proud, means that sleeves and cuffs in particular snag on it. Far less of a problem with the SRPE

or indeed a more modern Seiko diver which has usually got a shape that will allow the watch to deflect the cuffs of shirts up and over it.

(image sourced from Reddit)

Accordingly the bezel gets caught on sleeve which is annoying, so this feels like its going to be more of a summer watch to me. However I'm still wearing it a day later so ¯\_(ツ)_/¯

Lastly we come to the fact that now most divers (not the Seiko 62MAS, nor the Willard however) now have a screw down crown. Because its a mechanical watch its not going to be as accurate as a Quartz watch is, which means you'll probably be unscrewing that to be setting the time weekly (if we accept that its going to be something like 5 minutes a week out) or if you aren't wearing it daily every time you need to put it on. In the past my (still to this day) favourite daily diver was my Sports 100 from 1979 (which I bought in 1983 or so)

As you can see:

• its very slim
• its very light (less than 63g the Seestern  was 66g)
• the bezel allows finger grip but shirt slip

Being quartz it only required me adjusting the date every now and then because the time was accurate to seconds per month. Frankly adjustment of the date happened infrequently because I often never referred to the date; the day however I looked at frequently but never needs adjustment (unlike the date of the month). So the crown would be unscrewed perhaps 4 times per year. Meaning unlike my Seestern it will never suffer stripped or worn crown case tube threads over time. 

Note also that the Sports 100 has excellent legibility and very clear quarter hour markers; making it an excellent watch from many angles.

Conclusions

Basically the Seestern MAS deserves to be a daily wear watch (the disrespectful will use the term "beater") because:

• its very economically priced (like not far from a Casio Duro)
• it has a robust and reliable NH35 movement in it (so, not unlike that in my SRPE

I'm very pleased to have this watch in my box and I hope that come summer it'll see more time than my SRPE does ... 

I'll update this as I discover more. Update 1