statistics – What is the meaning of Delta in the discrete sample size formula?

The following excerpt is taken from the Six Sigma Institute website

Six Sigma Sample Size Formula - Discrete Data

I can’t understand what Delta represents in this formula.

First, considering example (2) on their page, they have used this formula to calculate that a sample size of 865 is required in order to estimate proportion defective to within 2%. For this to work you need a handle on the defect rate to begin with, which they have estimated as 10%. OK… so does this mean that with a sample size of 865 I should expect defect rates somewhere between 8% and 12% in practice?

If this is true, then I can’t understand example (1). If I plug these values back here to get delta (n = 865, P = 0.1) then I get a delta value of 50.

I am obviously completely misunderstanding this formula.

Transaction size limit across a single path in a Lightning Network and fee earned

Given MPP is included in the current version of lnd, an arbitrarily large transaction can be processed in the network. What is the transaction size limit across a single path? Is it still bounded to 0.0429 BTC (limited by max_concurrent_htlc)? What is the estimated fee earned (average as well as maximum) by a lightning node per day?

python – How to group every other unique value in pandas dataframe outside top 5 values (by size) into an ‘Other’ category for plotting and tabling?

I have a column Order with over 75 unique values of items (Clothes, Appliances, Electronics, etc.) and over 1000 entries in total. When I try to plot any descriptive statistics on a graph over a period of time (important: not all order items are non-zero in all periods of time), it becomes hard to read the graph because of how small some of the values are in comparison to others.

For that reason I think it would be better for me to just show the values of the top 3-5 order items (by size/count) and then group the rest into a category called Other just for plotting and groupby/pivot tabling purposes.

I guess I could map the values, but that is too time consuming, and it would also require me to change the existing values for the non top 3-5 represented entries – which is not something that I want to do.

How would I do that?

database size – What (kind of) DB can store store variable-length blobs without padding?

I have an offline task: store a HUGE amount of variable-length binary data on multiple hosts. Average data size is about 16Kb, total size: maybe hunderds of Tb. I have no consistency or speed requirement as it will likely have 1 client only.

When doing an interface mockup, I used SQlite and found this: when data pieces were all of the same length, the db file was only 4% larger than the raw data, but when I added variable-length data, the DB became almost 50% bigger. So it obviously uses some padding or reserving, and I don’t want to waste space like that.

Are there free databases that are known to be most efficient in terms of space for storing variable lengths of blobs? And provides an easy way to spread data across multiple hosts at same time?

Design of a single microservice, size limit?

I’ve been struggling for a while of what would be the “recommended” approach for a microservice itself.

There are quite of top architecture designs that are the holy sacred for a lot of craftsman devs, such as CQRS, Hexagonal, DDD, etc…

But from my point of view, depending of how “big” is the microservice, because you know the word itself it’s giving you a hint… “micro”!!

Should I consider build all the packages, interfaces, divisions between layers such as Hexagonal, or split the content of the microservice based on DDD (its supposed that 1 microservice its 1 domain??? if not… 😐 kind of WTF??)

Or just keep it on its essence like split the entrypoints(rest,queues)-core(business logic)-outpoints(DB,queues, or whatever) and let it open for a “little” extension.

If its too big, think on a split? In order to avoid “minimonolits” and what would be the limit to consider an “app”/API a microservice or a little monolit?

Maybe to be more clear.


├── Product
│   └── DDD/CQRS/Hexagonal stuff
|       └── ....
├── Sells
│   └── DDD/CQRS/Hexagonal stuff
|       └── ....
└── Customer
   └── DDD/CQRS/Hexagonal stuff
       └── ....

Microservice with basic crud -> Product-Sells-Customer(with patterns such as CQRS, Hexagonal, etc…?) -> Its a minimonolit for me.

The kind of what I look forward…

Gateway microservice
├── Product
│   └── routing stuff
|       └── ....
├── Sells
│   └── routing stuff
|       └── ....
└── Customer
   └── routing stuff
       └── ....


Product Microservice
├── Product
   └── Basic separation layer(REST/SERVICE/ORM-QUEUE)
       └── ....


Sells Microservice
├── Sells
   └── Basic separation layer(REST/SERVICE/ORM-QUEUE)
       └── ....


Customer Microservice
├── Customer
   └── Basic separation layer(REST/SERVICE/ORM-QUEUE)
       └── ....

The previous ones should have patterns such as CQRS, Hexagonal, etc…???

css – Why should “cancel” and “confirm” button have the same size?

Cancel and Confirm typically just happen to have same size buttons. There’s really no UX principle supporting same size primary and secondary buttons

In fact, a larger confirm button is preferred to emphasize the primary action. This is why a lot of cancel and undo actions on the web are styled as a link (e.g. UX.SE’s post answer form) to give the primary action more weight.

You can read more about visual weight from the article referenced by @DasBesto

Then why are cancel and confirm buttons usually the same size?

  1. The word “Cancel” and “Confirm” have very similar length.

Buttons length by default are determined by the length of its content. Since Cancel and Confirm are very similar in length, you get similar size buttons.

  1. Buttons on touch screen needs to be large.

On a mobile device, you need large tappable buttons. With a modal, to facilitate tapping, you make the buttons span the entire width. Cancel and Confirm are made the same size as a compromise to ensure both buttons are easy to tap on. This is okay because color also provides strong visual weight. As long as your Confirm button color make it stand out from your Cancel button, having the two button be the same size isn’t that big a deal.

gui design – When creating a GUI wizard, should all pages/tabs be of the same size?

Wizard vs. Tabs
Use a Wizard, when you want to guide the user through multiple requried steps.
Use Tabs when the user can select an arbitrary tab, make changes, and then commit them without looking at the other tabs.

I always find “Tabs with Back/Next” awkward. I understand the idea to provide a little “ramp” between novice and advanced users, but in most cases I’ve seen, the design of the individual pages isn’t suitable for novice users.


For a wizard, it’s not just size – the user should have the impression he interacts with the same window all the time. This is commonly achieved through a header and other control elements in the same position throughout all pages, and same size.

Example: Installshield violates the “same window” metaphor pretty badly (though it’s not too obvious): each page is a new modal dialog, centered on the primary monitor. So move the window to another position, click next, and bam, your window is back where it was. Aaaargh!

In a wizard, a changing form size is quite awkward for users. It’s like holding his hand, but you are constantly dancing around him. In more serious terms: the user action (clicking “Next”) has an unexpected side effect (“Window size changes”). This decreases the users perceived control over the software.

I’d argue that even for tabs, changing sizes are awkward. First, it looks shitty – which subjective. Second, if you position the window containing the tabs so that they are in the corner of a screen to reveal another document on your desktop, an you switch to another page, either part of your dialog vanishes, or it jumps further into the desktop, potentially covering other things.

(Full disclosure: I am working on an app which does that, and it’s my fault. Watching users pull around that poor little dialog makes me cringe. It’s one of those little speed-bumps that build up annoyance).

If the choice is between “a little crowded” and “almost empty”, it’s usually fine. Empty space looks good. Just having a large prominent window with a single input field makes a clear statement: this is your next step, and it’s darn easy. That’s exactly the message you want to send with a wizard.

Why do tempdb spills still occur even with good row and data size estimates (better than actuals)?

We’re seeing tempdb DB spills for some hashing operations. If the estimates are indeed good as shown what would be the next thing(s) to look for? Looking for a generic answer without having to resort to the specifc query.

This is part of an SP. Just switched to 2019 version to see if it would auto adjust but still getting spills so far.

Microsoft SQL Server 2019 (RTM) – 15.0.2000.5 (X64)

Hash Match Warnings