I’m baffled – trend reverses in direction when data is subsetted? Simpson’s Paradox in effect here?


I’m comparing May’s data to April’s for some stuff at work and something very curious has happened. We are looking at average time spent on one process. This is the same process everytime, however we can subset it into 2 (almost equal) sets.

When subsetted, both subsets are trending upwards from April to May, however when combined the entire set is trending downwards?

I had a google and the only thing that came up was Simpson’s Paradox (https://en.wikipedia.org/wiki/Simpson%27s_paradox), however I don’t think that applies here.

Any ideas? This is truly baffling to me

Edit: Here’s the plot for April and May: https://imgur.com/U2gLjOh

submitted by /u/LbrsAce
[link] [comments]

I test drove the new Mitsubishi Eclipse Cross – My thoughts

While I was taking care of a few things around town in my 03 Outlander, I noticed an Eclipse Cross out in the wild. I thought to myself,

“Oh, they finally released it eh?”

So as I sat down to eat a meal I did some research on it. Seeing the, to some, iconic Eclipse name come back on something other than a 2 door coop is a risky move. But I did recall Mitsubishi saying at one point that from 0-60 it would be faster then the Lancer – Something I didn’t believe back then, and can confirm now.

I called my local dealer and set up an appointment with one of the sales rep, who over the phone straight up told me that it was not going to be a car I would like. I thought to myself,

“I’ll be the judge of that.”

Mitsubishi resigned themselves to making almost only cross overs for the last few years, a move that other car companies like Ford are just only now doing. Surely since they’ve been doing it longer than most they know how to do it right….right?

I got to the dealer. Once look at the rear and right away, I knew there was trouble. The “spoiler” for the car ran ALL the way through the center of the rear windshield from left to right. Visibility was going to be an issue. But thats just one thing. Lets dive into the rest.

a 1.5L turbo with a CVT pushing just over 150HP.

Now, to some, that’s a turn off right there. BUT, in my mind this wasn’t inherently a deal breaker. Small engines with forced induction is a common thing now a days, and so long as there isn’t horrid turbo lag, they can be rather peppy despite the small displacement. And CVT’s, when done right, can actually be really good. (I point to the Nissan Juke a lot as an example – the CVT in there can keep super aggressive ratios to make the absolute most of their 1.8L engine and is surprisingly fast all things considered)

However, it was apparent immediately that this engine and CVT were not fit to bear the Eclipse name.

There is a very very tiny amount of turbo lag at low RPM with starting from a dead stop. But that means the turbo is really small too. something that makes sense given the 1.5L engine. There’s not going to be enough pressure to spool a big or even medium sized turbo, so small is the only way to go. So that means low amounts of boost at best. Hence the 150~HP.

Well, that doesn’t mean it can’t still be peppy. With a good CVT it can help make up for some of the lack of power. But alas, the CVT does the ONE thing that no CVT should EVER do –

it “simulates” fixed gear ratios. The benefit of a CVT is the almost infinite ratios in which to run, making the engine more efficient at any given speed or desired driving style – economic or aggressive. Lets not forget, the CVT has its roots in F1 racing. it can and is a good option when done right. But its obvious what happened.

the engineers wanted to make a good CVT – But marketing wants it to sound like it has gears because some people don’t like the droning sound it makes. The legal team needs to meet emission standards. So a compromise was made.

The CVT will pretend to have fixed ratios weather you like it or not. and thats NOT how to make an effective CVT. The only time i give a pass on this is with chain driven CVT’s. They do actually have a reason why they can’t be seamless like belt driven ones. I believe Subaru has Chain Driven ones, which is how they managed to use it with a turbo diesel in countries outside the USA. Those can handle more torque, but have a more limited range of ratios.

this is not one of those cases.

The Eclipse Cross uses an under powered engine, with a misguided CVT in a chassis that has viability issues. Whats worse – They used the Eclipse name on this thing. The only thing they could have done worse was use the Lancer name on it.

Their 4 wheel drive version has a set up that can only be described as stupid. They don’t call it 2 wheel, 4 wheel and 4 wheel locked. Its road, gravel and snow…

The electric power steering is like most – you can’t feel the road very well.

comfort in the back according to my friend is terrible due to the head rests.

over all, this car embodies everything that come from people who say that Mitsubishi is not going to be around in the USA much longer.

I fucking love Mitsubishi, but I can tell they are going to lose big time investing in this car. It’s an utter betrayal from what I expect from this brand.

Mitsubishi, if you EVER find this post, heres what to do.

If you are EVER going to use the name Eclipse or Lancer on another car, you NEED to use a 2L Turbo. You have made some of the best 2L turbos ever made (like the 4G63T). Stick with what you’re good at. At the same time, you are partly owned by Nissan now. Get them to show you how to make an aggressive CVT that preforms better than it sounds. Don’t pull that crap in a car with these names. Let the CVT do what it was MEANT to do. And last, if you must make a cross over, don’t make it just another grocery getter. The first gen Outlanders (not including the Airtrek) Had ground clearance, suspension travel, decent power (hell, you put the 4G63T in there with a 5 speed manual All wheel drive in Germany!!! Why not the USA???)

You know how to make a good car. Don’t fallow that pack – LEAD it. Cuz now, you’re falling behind and fast.

submitted by /u/ObsidianWraith
[link] [comments]

Book on some topics

I’m looking for some books/reference notes about a few things. I’m trying to understand the CPT theorem in axiomatic quantum field theory. If possible, I would like some recent references (2000+), but since it’s an old subject that may be hard to find. The standard reference I’m already using is PCT, Spin and Statistics, and all that by Streater and Wightman, but that’s a book from 1964, so it’s rather old. If anyone knows of a more recent book where it’s explained, it would be very much appreciated. The topics that I need most right now are:

-A reference on distribution theory, especially the Schwartz nuclear/kernel theorem. -A reference on the representations of the Poincaré group, but using more recent notations and such. -and, if it exists, a recent reference on just the Wightman axioms themselves.


submitted by /u/Migeil
[link] [comments]

Another set theory problem I solved. At least I think I did because the book gives me a different answer.

Write the following in set-builder notation. (π means pi)

{…, -π, -π/2, 0, π/2, π, 3π/2, 2π, 5π/2, …}

My answer: {cos-1(x) : x∈ℤ, -1≤x≤1}

The book’s answer: {kπ/2 : k∈ℤ}

I see my answer as being able to generate all those elements of the set given. Or am I mistaken? Did I miss something? Am I correct? Are we both correct? Opinions please.

submitted by /u/bootleg42
[link] [comments]

Hypothesis testing, help with T table

I have my econ stats final tomorrow so I’m just going over some past exams. Most the stuff I’m okay with but this one question has confused me.

Random sample of 16 and it wants to test the. Validity of the statement at 5% significance and at 1%.

Because the sample is less then 30 I use t’n-1, and so at 5 percent I’m testing it against 2.131 and at 1 percent against 2.947, however in the markschemes its using the percentages for 10% and 2%,

Only thing I can think of its because its one tail not 2 tail, but then do I just double the significance to make it one tail?

Any help? I can upload some pictures of the question and markschemes if needed.

submitted by /u/SalmonMan123
[link] [comments]

Super common question about Likert scales

I need help so desperately. So here’s my problem: I need to use three independent and one dependent variable to give insight on a research question, using SPSS. However, ALL my variables are likert scales. I figured I might just use chi square for all of them since they are categorical. But since this is a very big data set they all turn out significant with very high standardized residuals so I basically get no actual results.

My question is, could I treat them as interval/continuous and run a regression analysis? Would I need to make all of the independent variables into binary variables? What about the dependent variable? Would that also have to be a binary variable? They are, as I said all likert scales so I could for example make it into 0= strongly agree, agree 1= neither agree nor disagree, disagree, strongly disagree.

Would Anova be better? But it seems like those also all turn out significant. In regression analysis I would also get the R2 value which would at least tell me how well we can explain the result. Or is there another way to see how strong an association is in Anova, other than significance.

What would you do? I would appreciate your help so much.

submitted by /u/LeylaOmega
[link] [comments]