Hi /r/statistics, I’m looking to take a stats course, but my math background is pretty minimal. I worked for an accounting firm so I’m comfortable with spreadsheets, ledgers, projections, etc… but, I badly need an algebra refresher and I’ve never even taken calculus. Is there a (free?) online course that is good for people with my background? Or do you recommend taking some math courses before even diving into stats? Thank you! submitted by /u/ooftaxes123 [link] [comments]

## Bought a 26 year old automatic Mazda. AC is uncontrollable, but she had decent mileage and now she’s mine! [OC]

Album: https://imgur.com/a/STWBeQp

I BOUGHT MY DREAM CAR! 1992 JDM Efini FD3S RX7 Touring X, almost completely stock, with around 27,000 original miles and one previous owner in Japan.

This is my first non front wheel drive sports car and first time driving a rotary and first time driving anything faster than a 2012 Skyactiv Mazda 3. Quick review of my automotive outlook as of day two of driving my RX7.

- 1: I get turbos now
- 2: I really get the sequential twin turbo
- 3: I get rotaries more than I even thought I would
- 4: why would anyone need a faster car I literally cannot comprehend a faster acceleration
- 4.5: how are you even supposed to redline it, I hit the gas and then am already going traffic speeds
- 5: I barely fit what the heck, I’m 6’3” and I can’t turn the wheel without hitting my knees with my hands
- 5.5: I might be keeping my Mazda 3 longer than I thought, not sure I can commit to having this car completely “daily-ed” due to fitting in this car (but you but I’m driving it every day regardless)
- 6: oh my god I get LSDs now too, also I DON’T HAVE TO UNDERSTEER EVERY CORNER OR SET MY REAR SWAYBAR * TO STUPID STIFF TO SLIDE IN A BARELY CONTROLLED OVERSTEER

The car is almost completely stock save for an aftermarket head unit, though it’s around .5 inches lower in the front and 1 inch lower in the rear than reported stock numbers (trying to figure out if it’s on aftermarket springs like the Eibachs everyone loves, or if they were cut (hopefully not), or if the automatic just weighs that much more, which it does, but I don’t think it would be enough to lower the car thaaaat much and I also can’t seem to find if anyone else with an auto reported that ride height difference).

Regardless, I did change the turn signal and running light combos to Depo style lights and changed the JDM side markers to black ones. I have a few plans for interior materials upgrades, as well as light and reflector changes on the exterior, and modernizing the infotainment. But I don’t have plans to change to the ’99 spec bumper and spoiler like everyone tends to do, I’ve fallen in love with the car pretty much as is which is a big surprise as I’ve always been an aftermarket guy. But if anything aftermarket happens to this it would be VERY low key and reversible. I’d never actually seen a stock example before I bought my own and it really just IS that perfect as is.

Finally backstory if anyone has read this far without getting bored. This car is a few years older than I am, I realized this summer that I’m at the point in my life now (single (very very single), job security, inexpensive food and housing tastes, living in a city with maybe the best public transportation and bike paths in the US, and splitting rent with a billion roommates) that I could import a JDM RHD RX7 before the price sky rocketed further or I got tied into the whole “dating and marrying another human being and starting a family with a minivan thing.”

In the span of a couple months I found a (legal) importer (will name him if anyone is curious ’cause he was GREAT, just didn’t want to get flagged as advertising), bid on the car, won the car, shipped the car, got it registered and insured in the US, and am now driving it. I’d recommend the Japanese auction route to a friend, if you’re even ok with RHD. The prices I was bidding on this one and other ones I lost on were definitely more fair than the US market prices with the exception that you won’t know compression numbers (to be fair that’s a huge gamble and I still need to get mine tested this week though it feels totally all right).

The importer culled my “buyers goggles” (there’s a lot of junk out there he steered me away from), and when this car popped up, even though it was automatic I took one look at the pictures and the mechanic’s appraisal and bid everything on it. I ended up winning it for around 60% of the price of a similar mileage R1 (if anyone is curious on the price difference for an auto vs a manual). The difference in cost can eventually go to manual swapping it, but I’m not worried about that right now. The main “flaws” are scratches on the dashboard, an AC unit that works but does it’s own thing randomly, and that aftermarket head unit. And of course the fact that you can’t see it while driving it.

I’m going to go drive again. Thank god gas is cheap right now.

submitted by /u/rck_mtn_climber

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## Questions about a “taxicab” metric on a triangular grid and extension into three dimensions.

What would the “distance formula” be for an analog to a taxicab metric on a triangular grid instead of one with perpendicular axes? For the latter, with two points (x1,y1) and (x2,y2), it is simply |x1 – x2| + |y1 – y2|, but I’m having an extremely hard time coming up with a coordinate system that I can work with for the former. For example, if I consider using two axes at 60 degrees instead of 90 you get asymmetries like the distance between the origin and (1,0), (0,1), (-1,1), or (1,-1) is 1, while (1,1) or (-1,-1) are 2 away from it. I tried experimenting with having three symmetric coordinates but then it seems I can get points with two different valid coordinates. For example, if I set the axes clockwise around a hexagon as such: +x, -y, +z, -x, +y, -z, the “points” (0,0,0), (1,1,1), and (-1,-1,-1) all represent the same one, and I’m not sure how or if I can make a distance formula that would treat them all the same.

Also, I was wondering if such a metric could be extended to three dimensions. In two dimensions the unit ball for the perpendicular axes “taxicab” metric is a square “diamond” with vertices +/-1 along each axis, while its 3d analog is an octahedron, and the distance formula has an easy generalization as |x1-x2|+|y1-y2|+|x1-x2|. In the 2d “triangular” one the unit ball is a hexagon, while in a 3d analog I envision it being a cuboctahedron, as the 2d one has axes coinciding with the edges of a triangle, the 3d one might have axes corresponding to the edges of a tetrahedron. That seems like it would be even more difficult to come up with a distance function for.

submitted by /u/HexNash

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## Linear regression very significant βs with multiple variables, not significant alone

Could anyone provide intuition on why for y ~ β0 + β1×1 + β2×2 + β3×3, β1 β2 and β3 can be significant with a multiple variable regression (p range 7×10-3 to 8×10-4), but in separate regression the βs are not significant (p range 0.02 to 0.3)? My intuition is that it has something to do with correlations, but not quite clear how. In my case variance inflation factors are

## Weibull, inverse gaussian, or bath tub?

So today at work, I was describing, to a co-worker, the failure rate of a commonly used valve that very clearly has a “bath tub” curve. He took it a step further and called it inverse gaussian. Would calling it a weibull distribution not be more correct?

submitted by /u/Maroonedit

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## Interesting Series Summation involving prime numbers

Hi all,

I’m a big fan of prime numbers (Huge conversation topic at parties, I know). Anyways, I was playing around with the fact that Sexy Primes have twice the density of Twin/Cousin Primes, and how often twin primes appear in primordial sieves to come up with the following formula:

Note: I do not have any math education above a high school degree, so I apologize for the notation errors.

4 = 4/9 + [4/9 * 8/11] + [4/9 * 8/11 * 10/15] + [4/9 * 8/11 * 10/15 * 14/17] + [4/9 * 8/11 * 10/15 * 14/17 * 16/21]….etc. continued for all primes to infinity

Where each term in the series follows the following rule = [Prime^{Nth} – 3] / [Prime^{Nth+1} – 2]

Have you guys seen this before? Thanks!

submitted by /u/numbpie

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## Euclidean geometry : complex numbers :: a nonEuclidean geometry : ???

I’m watching this video which really made clear to me why imaginary axis is at a 90 degree angle to the real axis (it seemed like it could be an arbitrary decision)– it made the algebraic understanding of complex numbers fit with a geometric one.

This gives me some sense of a “naturalness” of Euclidean geometry, but I know that’s silly and there are multiple nonEuclidean geometries which are just as valid. Are there, then, any correspondingly different “natural” sort of algebras with those geometries?

submitted by /u/6point626e-34

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