Cancer Genomics Tools from Washington University (WUSTL) includes a list of R functions that can be used for various statistical tests.
UCLA's Academic Technology Services department has a page with R links and information. In particular, they have a list of analyses and sample code.
Friday, July 17, 2009
Wednesday, July 15, 2009
Dunbar's Number and Security
Post by Bruce Schneier on his blog, "Security, Group Size, and the Human Brain"
In a 1992 article, Dunbar used the correlation observed for non-human primates to predict a social group size for humans. Using a regression equation on data for 38 primate genera, Dunbar predicted a human "mean group size" of 148 (casually rounded to 150), a result he considered exploratory due to the large error measure (a 95% confidence interval of 100 to 230).
Several layers of natural human group size
3-5: Clique - people you would turn to in times of severe emotional distress
12-20: Sympathy group - people with whom you have special ties
30-50: Typical size of hunter-gatherer overnight camps
150: Approximate maximum number of co-workers
500: Megaband
1500: Tribe
Note: All of these numbers have very large confidence intervals.
These numbers (and particularly the ~150 number) are important because of their effects on organizational behavior.
Coherence can become a real problem once organizations get above about 150 in size. So as group sizes grow across these boundaries, they have more externally imposed infrastructure -- and more formalized security systems.
Small companies can get by without the internal forms, memos, and procedures that large companies require; when does what tend to appear?
In a 1992 article, Dunbar used the correlation observed for non-human primates to predict a social group size for humans. Using a regression equation on data for 38 primate genera, Dunbar predicted a human "mean group size" of 148 (casually rounded to 150), a result he considered exploratory due to the large error measure (a 95% confidence interval of 100 to 230).
Several layers of natural human group size
3-5: Clique - people you would turn to in times of severe emotional distress
12-20: Sympathy group - people with whom you have special ties
30-50: Typical size of hunter-gatherer overnight camps
150: Approximate maximum number of co-workers
500: Megaband
1500: Tribe
Note: All of these numbers have very large confidence intervals.
These numbers (and particularly the ~150 number) are important because of their effects on organizational behavior.
Coherence can become a real problem once organizations get above about 150 in size. So as group sizes grow across these boundaries, they have more externally imposed infrastructure -- and more formalized security systems.
Small companies can get by without the internal forms, memos, and procedures that large companies require; when does what tend to appear?
Tuesday, July 14, 2009
Machine Learning Resources
Stanford University CS229 (Machine Learning) Materials
- Andrew Ng's presentation - ML Advice
- Problem: Overfitting (high variance)
- Diagnostic: Training error is much lower than test error
- Solution: Larger dataset, fewer features
- Problem: Too few features (high bias)
- Diagnostic: Training error is high
- Solution: Larger set of features, different features
Wednesday, July 8, 2009
Great analogies for wireless security
From a Lifehacker.com article
- WEP is like a home bathroom lock, the one you can open just using a bent paperclip. Everyone knows how to unlock it, but when it's locked everyone who walks by understands they should stay out.
- WPA is like a standard door lock; it's a lot more secure, but it is still possible to get by for someone with the right tools, knowledge, and circumstances.
- WPA2 is like a bank safe. It may be possible to defeat, depending on how it's been set up, but it's not realistically possible for anybody to actually do so... yet.
- Not broadcasting your SSID is like taking the numbers off of your house - The house is still there and everyone can see it, it's just a bit harder to find for people that don't know what they are looking for already.
- Filtering by MAC address is like having a guard at the door that checks everyone's name against a list to see if they can enter. The only problem is, he doesn't ask for ID or remember what people look like, so anybody can and can listen in to see what names are allowed and then claim to be anybody else.
Monday, June 29, 2009
Facebook vs Google - Social vs Objective
Wired.com article titled Great Wall of Facebook: The Social Network's Plan to Dominate the Internet
For the last decade or so, the Web has been defined by Google's algorithms—rigorous and efficient equations that parse practically every byte of online activity to build a dispassionate atlas of the online world. Facebook CEO Mark Zuckerberg envisions a more personalized, humanized Web, where our network of friends, colleagues, peers, and family is our primary source of information, just as it is offline. In Zuckerberg's vision, users will query this "social graph" to find a doctor, the best camera, or someone to hire—rather than tapping the cold mathematics of a Google search. It is a complete rethinking of how we navigate the online world, one that places Facebook right at the center. In other words, right where Google is now.
How would you rather get information? An objectively defined "best"? Or a recommendation from a trusted friend? Are they truly mutually exclusive?
"Up until now all the advancements in technology have said information and data are the most important thing," says Dave Morin, Facebook's senior platform manager. "The most important thing to us is that there is a person sitting behind that keyboard. We think the Internet is about people."
For the last decade or so, the Web has been defined by Google's algorithms—rigorous and efficient equations that parse practically every byte of online activity to build a dispassionate atlas of the online world. Facebook CEO Mark Zuckerberg envisions a more personalized, humanized Web, where our network of friends, colleagues, peers, and family is our primary source of information, just as it is offline. In Zuckerberg's vision, users will query this "social graph" to find a doctor, the best camera, or someone to hire—rather than tapping the cold mathematics of a Google search. It is a complete rethinking of how we navigate the online world, one that places Facebook right at the center. In other words, right where Google is now.
How would you rather get information? An objectively defined "best"? Or a recommendation from a trusted friend? Are they truly mutually exclusive?
"Up until now all the advancements in technology have said information and data are the most important thing," says Dave Morin, Facebook's senior platform manager. "The most important thing to us is that there is a person sitting behind that keyboard. We think the Internet is about people."
Tuesday, June 2, 2009
Just Don't Look
Do I want to hear about the latest sob story on the nightly news?
Do I want to know what J. Lo or Brad Pitt or [insert celebrity of choice] is up to?
Do I care about the latest weight-loss approach? (Seriously, just burn more calories than you eat, or eat less calories than you burn - how hard is that?)
This post at Coding Horror, which references this post at kottke.org, describes an approach to dealing with things/people that run on attention - Just Don't Look.
That's how you change the world. Not by arguing with people. Certainly not by screaming at them. You do it by ignoring them.
Do I want to know what J. Lo or Brad Pitt or [insert celebrity of choice] is up to?
Do I care about the latest weight-loss approach? (Seriously, just burn more calories than you eat, or eat less calories than you burn - how hard is that?)
This post at Coding Horror, which references this post at kottke.org, describes an approach to dealing with things/people that run on attention - Just Don't Look.
That's how you change the world. Not by arguing with people. Certainly not by screaming at them. You do it by ignoring them.
Monday, June 1, 2009
How to defuse a "Screw-Me" moment? (Hint - "Spin" is the wrong answer)
Blog post at Rands in Repose
Manage the room. Questions aren’t Screw-mes. You can clarify and stay on track. You know that Amanda is going to ask about hard data, right? Don’t let her take over the conversation. Say, “I’ve got your data in the appendix, but let me get through this first, ok?” Yeah, you just shut down a Senior VP. Nicely done. No way you can do that without serious confidence in your preparation. Yes, Tim?
Tim’s got the Screw-Me and you didn’t see it coming. Total left field. Completely valid strategic observation and you don’t have a clue how to answer. Shit.
You will recognize the Screw-Me by the complete silence that fills both the room and your head. That’s the realization everyone is having that you’re Screwed. First, let’s not make it worse…
Tim: “Rands, what about THIS?”
I’m a poker player and an experienced meeting surfer, so the room will not immediately know from the look on my face that This has Screwed me, but what I choose to do next will define my ongoing relationship with the room.
There are two options when you are cornered by This. Your animal brain, when cornered, will try to find a way out. You can taste this approach even before you begin. I am going to spin. I am going to talk quickly and confidently about This and I am going to hope that in my furious verbal scurrying they are going to believe I’ve got This handled.
That’s not what they’re seeing or hearing.
This is not your staff meeting where a little verbal soft shoe is going to entertain and delight. These are the execs and no matter how many meetings you’ve surfed, they see straight through spin, they know this dance, and the longer you sit there spinning, the longer you give your boss an opportunity to step in, try to make the diving save, and make you look like a blithering fool.
It takes a little practice to make the correct move when you feel the spin coming. You are going to do three things:
Manage the room. Questions aren’t Screw-mes. You can clarify and stay on track. You know that Amanda is going to ask about hard data, right? Don’t let her take over the conversation. Say, “I’ve got your data in the appendix, but let me get through this first, ok?” Yeah, you just shut down a Senior VP. Nicely done. No way you can do that without serious confidence in your preparation. Yes, Tim?
Tim’s got the Screw-Me and you didn’t see it coming. Total left field. Completely valid strategic observation and you don’t have a clue how to answer. Shit.
You will recognize the Screw-Me by the complete silence that fills both the room and your head. That’s the realization everyone is having that you’re Screwed. First, let’s not make it worse…
Tim: “Rands, what about THIS?”
I’m a poker player and an experienced meeting surfer, so the room will not immediately know from the look on my face that This has Screwed me, but what I choose to do next will define my ongoing relationship with the room.
There are two options when you are cornered by This. Your animal brain, when cornered, will try to find a way out. You can taste this approach even before you begin. I am going to spin. I am going to talk quickly and confidently about This and I am going to hope that in my furious verbal scurrying they are going to believe I’ve got This handled.
That’s not what they’re seeing or hearing.
This is not your staff meeting where a little verbal soft shoe is going to entertain and delight. These are the execs and no matter how many meetings you’ve surfed, they see straight through spin, they know this dance, and the longer you sit there spinning, the longer you give your boss an opportunity to step in, try to make the diving save, and make you look like a blithering fool.
It takes a little practice to make the correct move when you feel the spin coming. You are going to do three things:
- Acknowledge the Screw-Me.
- Admit “I don’t know.”
- Concretely explain the steps you’re going to take to find out and give yourself a deadline.
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