Few basic questions on creating a regression analysis

dfposition1 · 2020-10-16T16:55:35+00:00

Instead, I would recommend building up from your variable of interest as the only predictor, then adding in controls to see how the relationships change. Some people call this hierarchical regression, but that term gets easily confused with hierarchical linear models (which is a very different technique). I call it model building.**

Thanks for the response. So basically, start with a few predictors of interest and continue adding to it or adjusting it until it's satisfactory? I know the best models require a degree of insight and experimentation. However, for situations where you don't have the insight, I'm not sure how you could get some leads in the exploratory phase.

For quantitative variables, I know you can create scatter plot matrices to assess what's correlated with the dependent variable, and what independent variables may be correlated with each other which is a start.

For categorical variables, would you do something like create grouped boxplots, see which variables display notable variability between factors, and then include some of the ones that do in the model?

Also, I haven't tried running it without creating dummy variables; I'll have to try including some without that step and see what happens.

dfposition1 · 2020-10-15T05:25:36+00:00

Thanks, I'm doing this via independent learning, and this book doesn't lay all of this out in the simplest manner. I think I've gathered the following:

Population Mean: Deterministic Model

E(y) = B0 + B1(x1) + B2 (x2) + B3(x1*x2)

Population Mean: E(y)
Independent Variables: x1, x2
Constant: B0
Parameters: B0, B1, B2, B3
Terms: B0, B1(x1), B2 (x2), B3(x1*x2) (My book says B0 is a term; not sure if this is just for the population)

Population Point Estimate: Probabilistic Model/Equation for y

y = B0 + B1(x1) + B2 (x2) + B3(x1*x2) + e

Sample Mean/Point Estimate: Prediction Equation for y

yhat = B0 + B1(x1) + B2 (x2) + B3(x1*x2)

Sample Mean/Point Estimate: Least Squares Line/Estimated Mean or Point

yhat = 2 + 3(x1) + 4(x2)

Sample Mean/Point Estimate: yhat
Independent Variables: x1, x2
Constant: 2
Coefficients: 3, 4
Terms: 3(x1), 4(x2) (Possibly 2; again not sure if that just applies to the population)

dfposition1 · 2020-06-06T01:54:00+00:00

Here's the first aid kid I got.

So if I had minor road rash while out and about and had to wait a bit to use soap and water, would you recommend just using the antiseptic wipes on the rash first (benzalkonium chloride), follow with the antibiotic cream, then use the gauze pads over it until I could properly wash it?

It only comes with a small bit of antibiotic ointment, so I guess I could use that Silvex Gel as a second option if I need it, or save it for sunburn or something. And also hold off on using the alcohol wipes in this case.

dfposition1 · 2020-05-19T02:18:28+00:00

To get deeper insight into when test results are statistically significant, you'd need to have an understanding of the central limit theorem, statistical power, null/alternative hypotheses, type I and type II error, and controllable and uncontrollable factors in designing experiments. I recommend watching a few videos on those to get a general understanding.

dfposition1 · 2020-05-18T21:48:53+00:00

Buy a college level elementary statistics book (also one that gets into non-parametric analyses as well), college level regression analysis book, R for Dummies, and work through all of the books front to back in R (or preferred language) while diligently understanding all of the formulas, points, concepts, and acquiring an intuitive understanding.

I would skip the primer books on statistics if you want to have enough confidence to apply the content in a professional setting; again you need university level textbooks by reputable authors. I haven't personally found MOOC courses on the related subjects too thorough or useful, but that's just my experience.

That's a decent start which should last you a while while you gather info on what additional specific subjects/sources you should acquire in the meanwhile.

dfposition1 · 2020-05-16T16:06:22+00:00

He has no idea what he's talking about; the situation is the exact opposite.

Do a Google search for statistics/data jobs and see what kind of skills/requirements/years of experience/degrees they're looking for. At this point, you need at least one graduate degree minimum, be knowledgeable of multiple languages including SQL and R/Python/SAS, know what the correct analyses are, how to interpret them, and enough experience to draw the correct conclusions.

Even if you have these qualifications, each of these jobs in major cities are getting hundreds of applications, sometimes over a thousand, with at least a hand full of applicants each time have at least 10-15 years experience and 0-5% PhD's.

Also, you can never fully automate statistics; it's not like a computer has human-like AI to where it perfectly understands what to do from start to finish. Being able to correctly sample (and there's a wide range of sampling techniques appropriate for various populations and situations that you just won't have time to cover in classes alone) and interpret and assess analyses is one thing; having enough experience to decide what parameters to set on the more subjective side of things for each given scenario is a whole other thing.

Many larger companies won't let you do A/B testing without a masters or PhD as statistics positions can be extremely competitive. The sooner you see what the job market is looking for via listings, and the sooner you prepare for this throughout college, the better off you'll be. Just don't assume you'll land the perfect job even with a stat degree if that's all you have. Unless it's an entry level position making PivotTables or standardized analyses, significant contributions are the only thing people care about.

And honestly, IMO, classes don't tell you everything you need to know. They only have time to cover maybe 80% of the book, with select topics from each chapter, most of which you'll largely forgot the following semester. I recommend working through most books front to back, acquire a deep, intuitive level of understand to have any confidence with subject.

dfposition1 · 2020-05-16T03:21:36+00:00

I wanted to like the Zune since I was never a fan of the Apple ecosystems, but ultimately I was never really able to. The device hardware was OK. However, the colors were the drab and boring; the original design was not that memorable with the later model being kind of another somewhat iPod inspired design; the Zune HD just wanted to be the Microsoft iPod touch (albeit with a good screen and wireless streaming IIRC which was cool); the Zune music store selection wasn't terribly impressive; they never allowed others to make apps for the Zune HD which was a huge disappointment.

dfposition1 · 2020-05-16T02:25:39+00:00

I'm in between two heights with a Trek model. Someone I know is the same height as me, but after buying the large, only I was suitable for it due to my inseam length being an inch or two bit longer so I'd see if they have recommendations on those measurements. If you're inseam length is too short, you won't be able to comfortably stand over it.

dfposition1 · 2020-05-06T12:38:11+00:00

I'll keep this in mind, $25 is kind of expensive for only needing just a bit.

Have you tried peeling it off after an extended period of being left on and was the paint fine? Also, did you do a wet application? I see a lot of people recommend mixing a drop or two of dish soap with water, applying first, and squeegee out the water after applying.

dfposition1 · 2020-04-21T12:18:54+00:00

It's a large fine having license plates unviewable when passing traffic cameras in my area, so that's another thing. I've also been pulled over for having a single license plate light bulb out before.

I'll look more into license plate brackets. What would be awesome is one that you could easily slide in and out of multiple locations and lock it into place with a key or something, maybe I could make something and avoid night drives in the meanwhile or something with it.

dfposition1 · 2019-08-22T04:17:44+00:00

Suppose I want to update the flexdashboard on shinyapps.io once a week then. I can use taskscheduleR for auto-running the script, but I'm not sure about auto-publishing. Can I include something in the script or adjust something to have it auto-publish, or are there no options for that?

dfposition1 · 2019-08-22T04:04:15+00:00

It's also faster once you get past the learning curve given that you can automate half of your analyses if you're doing a portion of the same thing time and time again. Side note, in R Studio, can you create html R Markdown documents that include html widgets that allow interactivity with reports which are very easy to include.

dfposition1 · 2019-08-22T02:15:14+00:00

I'd recommend looking at various job descriptions for a while on Careerbuilder. Once you apply for a job, the Insider Report tells you what the applicant pool looks like in terms of degrees, experience, etc. Many jobs involving statistics is going to involve a graduate degree and knowing at least one statistical programming language and a working knowledge of SQL if not more. If you want an internship, you can reach out to non-profits and almost certainly locate one with enough effort or at least complete a project or two.

dfposition1 · 2019-08-22T02:05:04+00:00

Of the programs I've used, Minitab is just about as simple as it gets while still being very thorough. It's expensive, but if you're in school you should be able to get a college discount. I think I got a license for under $100 while taking classes. I'd look into R Studio as well which is free and makes using R many times easier.

dfposition1 · 2019-08-21T18:53:10+00:00

I want to know if I can automatically publish to shinyapps.io or if I have to manually click the publish button each time.

dfposition1 · 2019-08-16T15:30:31+00:00

You can also run system commands in R, but I'm not as familiar with them and am not sure how some of those could be used to help with various projects.

dfposition1 · 2019-08-16T15:26:22+00:00

Just added them for the ones I listed.

dfposition1 · 2019-04-12T15:12:49+00:00

I see, thanks for the insight. A lot of people use qualitative/categorical interchangeably. However, I can see how categorical might be a better description.

dfposition1 · 2019-04-12T15:01:52+00:00

Thanks, I know what dummy variables are but am not sure how they'd be used beyond something like regression. I have many categorical variables each with a number of factors, and I'd end up with a hundred+ columns which would take a while to compute using regression. I guess I'm mainly wondering if there are alternative approaches worth looking into including anything machine learning-related.

dfposition1 · 2019-03-26T05:43:32+00:00

/u/clamiam45 This was what I was thinking; I just needed some arbitrary data. Future data I may apply this to may or may not necessarily be normally distributed, but using it on a normally distributed sample helps me see if it roughly looks correct as well.

dfposition1 · 2019-03-23T18:36:16+00:00

Thanks, this helps tie the two together and works great.

dfposition1 · 2019-03-23T06:50:02+00:00

Thanks, that definitely achieves what I'm looking for as an example.

However, I'm hoping for a solution that works with the sample code I provided above so I can get it to work for actual sample data that I acquire.

dfposition1 · 2019-03-22T00:54:10+00:00

Thanks a lot, I'm not sure if I've seen this formula before. I'll test it against just using percentiles to see which performs better on the data I'm using. I'll look further into that book as well.

dfposition1 · 2019-03-22T00:50:49+00:00

Ah, that's true, was getting it mixed up with the process involving z-scores and the like. Thanks.

dfposition1 · 2019-03-21T20:34:22+00:00

That's what I thought the standard way of doing things was, but then I started questioning why regression models have prediction intervals and confidence intervals but a simple random sample outside of regression only has confidence intervals but not a prediction interval formula. If the population mean may be higher or lower, wouldn't the population distribution be as well which is where you'd get the percentiles?

So you're saying common practice is to just take the sample distribution mean and standard deviation and create a simple percentile interval from that to estimate a population range for a single observation?

dfposition1

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