Dealership problem. Advice wanted.

I’m in a unique and frustrating situation with a dealership and I’d like some advice.

At the end of January, another driver hit my Mclaren 650s. The damage to my car was primarily body damage. The Mclaren was sent to a well-known Mclaren dealership out of town for repair and I decided to have them do my annual service at the same time to save myself some time and another transporter trip. The repairs alone were approximately $60,000 and took until the end of April.

Upon delivery of the car, I noticed that they had not installed one of the parts that should have been installed and the car was giving constant ESC and control mode errors that shifted the car into limp mode until the car was restarted. None of the usual home remedies seemed to work, so I shipped it back to the dealer on May 2 to complete repairs.

On May 4, I get a call from my service advisor who explains that one of his techs was out testing the car and had wrecked the car. The initial story that was related to me was that the front left tire had entirely locked up, that the car began to swerve, the driver corrected but the front left impacted the center median followed by the rear left. Also, this happened in the rain… but the advisor, besides being nice and apologetic, was mostly focused on how lucky I was that this problem didn’t happen while I was driving. Ok.

Things happen, I didn’t yell or scream. I just asked that they repair the car completely and quickly. However, the more I thought about it, the less it made sense to me. Sure, it’s possible the front left locked up entirely, but how likely is that during normal driving conditions. The advisor also sent some pictures along in which both left side wheels are heavily scratched entirely around the rims (indicating to me that both were moving at impact). The front left wheel is entirely broken and the brake disk is shattered. That’s just the obvious damage I can see as a non-expert. The service advisor said it would take about a month to repair.

A week passes and I hear nothing, so I follow up. There is a lot of discussion about attempting to figure out the cause of the wreck but not a lot of information.

Another week passes with no information. So I follow up. The service advisor says that they’ve investigated the cause but can not find any mechanical cause. He doesn’t say it was likely his driver’s error, but… what else would it be, realistically? He then says that he’s waiting on insurance to order the parts and that is going to determine how long this takes.

That’s where I get frustrated. I realize that the dealership hasn’t even ordered the parts or started the repair two full weeks after they wrecked my car. In my opinion, as a non-expert, this is terrible customer service. They are basically punishing me by making me wait for their insurance to issue an authorization rather than ordering the parts they need now and letting the paperwork catch up. To be clear, there is no dispute who wrecked the car – it is the dealership’s responsibility.

I wrote him back, politely, and pointed this out. I also asked for a parts list of everything that would need to be repaired. I didn’t get it. Instead, the advisor said he isn’t sure what needs to happen to get insurance moving but that he would let his boss know.

We are now closing in on almost three weeks or one week from when he initially said the car would be complete. I have absolutely no hope that the repairs will be completed within that timeline and I’m really unsure what I should do at this point. I don’t think the service guy is being intentionally dishonest or particularly bad at his job – but I suppose if my company wrecked a $300,000 car owned by a relatively small community worldwide, I’d make every effort humanly possible to get the car repaired as quickly as possible.

Thoughts? Ideas?

submitted by /u/spect0rjohn
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Casting out nine trick doesn’t work.

Hi, I just learned a trick from a book “Things to make and do in the fourth dimension” by Matt Parker. The trick is described in the picture below.

As I understood, the trick works because of the casting out nines method. You take any number and add its digits together. If the answer has more than one digit, you repeat till it has only one digit. What you get is called the digital root of a number, it’s the remainder of the number after it has been divided by 9. The key of the “magic” is that when you multiply the original number by 9 , the digital root of the number (after having multiplied by 9) is always 9. You have the volunteer read out all but one digit of the number, from then you can easily find the missing number by calculating the difference between the digital root of all the digits read out by the volunteer and 9.

However, I ran into a problem when I tried to do the trick with 20 and 21. Let’s say I pick the number 20, 20 x 9 = 180, then I pick the digit 1 and 8. The digital root of 1 and 8 is 9. Difference between the digital root and 9 is 0, therefore the missing number is 0 (Yay!). This is correct but the problem emerges when I tried to do the same with 21. 21 x 9 = 189. Say I pick 1 and 8 again. I calculate the digital root and then confidently conclude that the missing number is 0. The audience boo the hell out of me. What’s going on here? Matt says that this trick works 100% of the time. Am I stupid or missing something here?

Thank you.

submitted by /u/ngqhoangtrung
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Statistical test for comparing populations means based on a big sample and a small one

I have some sets of data and I would like to compare their means.

For the moment I just calculated their means and compared them but I think that viewing each set as a sample of a bigger population and using a statistical test to compare their mean would be more appropriate.

I would like to hear some opinions regarding this approach.

Besides that, I am not sure what statistical test to use. I can’t say that these data sets follow a normal distribution. The data is continuous and some sets have a few hundred items but some have less than 10.

Could you please recommend a statistical test for comparing the mean of two samples for which one is sufficiently large (more than 30 items) but the other one has less than 10?

I was thinking about using a T test but since I can’t say that the populations follow normal distributions and the samples aren’t big enough in all cases, I’m not sure if that’s appropriate.

submitted by /u/IceVortex
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How to impute missing data using a predictive model?

I recently attended a talk about imputing missing data using machine learning and during the Q&A a random audience member commented that when using machine learning (or any predictive model) for imputation, we should use the resulting probability distribution to impute rather than the highest prediction probability.

From what I understand, the commenter was saying if the model says there is a 60% chance it is “A” vs “B.” Rather than assigning the missing value “A”, you should flip a weighted coin (60%/40%) and impute the outcome that way.

Can anyone explain the reasoning here? Wouldn’t it make sense to impute with the best prediction?

submitted by /u/Adamworks
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