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Day: September 3, 2021

Subgroup Analysis via Bayesian Hierarchical Modeling

Keith Goldfield ponders subgroup analysis:

Which got me thinking, of course, about subgroup analyses. In the context of a null hypothesis significance testing framework, it is well known that conducting numerous post hoc analyses carries the risk of dramatically inflating the probability of a Type 1 error – concluding there is some sort of effect when in fact there is none. So, if there is no overall effect, and you decide to look at a subgroup of the sample (say patients over 50), you may find that the treatment has an effect in that group. But, if you failed to adjust for multiple tests, than that conclusion may not be warranted. And if that second subgroup analysis was not pre-specified or planned ahead of time, that conclusion may be even more dubious.

If we use a Bayesian approach, we might be able to avoid this problem, and there might be no need to adjust for multiple tests. I have started to explore this a bit using simulated data under different data generation processes and prior distribution assumptions. It might all be a bit too much for a single post, so I am planning on spreading it out a bit.

Read on for two separate Bayesian model approaches to the problem. H/T R-Bloggers.

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Troubleshooting Microsoft.Purview not Registered

Wolfgang Strasser investigates an issue:

In my last Azure Purview Quickstart video (#3 – Create an Azure Purview Account – link), I’ve shown you how to create a new Azure Purview account.

And what pre-prepared demos have in common, well – it “just” works there 

BUT: there are some requirements that need to be configured beforehand, in order to create an Azure Purview Account.

Basically, problems during the creation process can be listed to:

– Security / permissions

– Missing Resource providers

Read on to learn more about permissions requirements and how to deal with these issues as they arise.

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Implicit Conversions and SARGability

Erik Darling bears bad news:

Data types are one of those core things you need to get right. Whether it’s matching types between join columns, or between parameters and predicates, not doing so can really squash application performance in quite similar ways to writing non-SARGable predicates.

That’s because — wait for it — a lot of the stuff we’ve talked about over the last week that can happen with poorly written predicates can happen with poorly matched data types, too.

Click through for an example. If this keeps up, we may never save Sarge.

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Where Databases Fit in the Always-Valid Domain Model

Vladimir Khorikov asks an important question:

Today, we’ll talk about an important question: how does the application database fit into the concept of Always-Valid Domain Model?

In other words, is the database part of the always-valid boundary or should you consider it an external system and validate all data coming from it?

Pre-read, my answer was no, databases are part of the external world and your domain model needs to validate every time because who knows what weirdo did something to your data while it slept.

Post-read, well, you’ll have to read to find out.

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Azure Database for PostgreSQL Replicas

Gauri Mahajan takes us through replica creation in Azure Database for PostgreSQL:

Azure Database for PostgreSQL is an Azure offering of the open-source Postgres database. As there are many databases and data warehouses that are derived from Postgres, during migration from Postgres to a different flavor of another database or data warehouse that is compatible with Postgres, often read replicas are employed. The replicas are read-only since it’s a one-way replication from the master database to replicas. And replicas serve the purpose of decreasing the load on the primary transactional database in production environments. Replicas are typically used as migration sources, reporting and ad-hoc analytics sources and for other purposes. Let’s go ahead and learn to create and manage read replicas in Azure Database for PostgreSQL.

Click through for the process.

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Comparing Objects in Powershell

Phil Factor has a new cmdlet for us:

Whatever your development methodology, you need to make changes lightning fast, and the easiest way of doing that is to test frequently. If you are driving this work with PowerShell, which works well, you’ll want to compare the actual results of a process with the expected results. You’re keen to see what’s changed but will often have no idea what to look for beforehand. You need the broad view.

Fine. To do this, you need something that can tell you the differences between two objects. Yes, there is already a cmdlet to do that called Compare-Object. It is useful and ingenious, and works well for what is does, but it doesn’t do enough for our purposes. Let’s run through a few examples, just to explain why I need more for many of the things I do.

Read on to see where Compare-Object could be better and Phil’s solution to the problem.

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