Dijkstra introduces the topic of his letter, which is that he has noticed that goto statements are mostly detrimental to the programs in which they appear.
Business Week recently ran an spoof article pointing out some amusing examples of the dangers of inferring causation from correlation. The standard scientific answer to this question is that with some caveats we can infer causality from a well designed randomized controlled experiment.
And, given that we can find more general procedures for inferring causal relationships, what does causality mean, anyway, for how we reason about a system? It might seem that the answers to such fundamental questions would have been settled long ago. In fact, they turn out to be surprisingly subtle questions.
Over the past few decades, a group of scientists have developed a theory of causal inference intended to address these and other related questions.
This theory can be thought of as an algebra or language for reasoning about cause and effect. Many elements of the theory have been laid out in a famous book by one of the main contributors to the theory, Judea Pearl. Although the theory of causal inference is not yet fully formed, and is still undergoing development, Conceptual modification essay has already been accomplished is interesting and worth understanding.
In this post I will describe one small but important part of the theory of causal inference, a causal calculus developed by Pearl. This causal calculus is a set of three simple but powerful algebraic rules which can be used to make inferences about causal relationships.
The post is a little technically detailed at points. However, the first three sections of the post are non-technical, and I hope will be of broad interest. You may find it informative to work through these exercises and problems.
Before diving in, one final caveat: I am not an expert on causal inference, nor on statistics. The reason I wrote this post was to help me internalize the ideas of the causal calculus.
Occasionally, one finds a presentation of a technical subject which is beautifully clear and illuminating, a presentation where the author has seen right through the subject, and is able to convey that crystalized understanding to others.
Nonetheless, I hope others will find my notes useful, and that experts will speak up to correct any errors or misapprehensions on my part.
You might think that we could conclude from this that being Republican, rather than Democrat, was an important factor in causing someone to vote for the Civil Rights Act.
However, the picture changes if we include an additional factor in the analysis, namely, whether a legislator came from a Northern or Southern state. If we include that extra factor, the situation completely reverses, in both the North and the South.
Democrat 94 percentRepublican 85 percent South: Democrat 7 percentRepublican 0 percent Yes, you read that right: You might wonder how this can possibly be true.
You can skip the numbers if you trust my arithmetic. In fact, at the time the House had 94 Democrats, and only 10 Republicans. The numbers above are for the House of Congress. The numbers were different in the Senate, but the same overall phenomenon occurred. If we take a naive causal point of view, this result looks like a paradox.
As I said above, the overall voting pattern seems to suggest that being Republican, rather than Democrat, was an important causal factor in voting for the Civil Rights Act. So two variables which appear correlated can become anticorrelated when another factor is taken into account.
You might wonder if results like those we saw in voting on the Civil Rights Act are simply an unusual fluke.
But, in fact, this is not that uncommon. In each case, understanding the causal relationships turns out to be much more complex than one might at first think. Imagine you suffer from kidney stones, and your Doctor offers you two choices: Your Doctor tells you that the two treatments have been tested in a trial, and treatment A was effective for a higher percentage of patients than treatment B.
Keep in mind that this really happened. Suppose you divide patients in the trial up into those with large kidney stones, and those with small kidney stones. Then even though treatment A was effective for a higher overall percentage of patients than treatment B, treatment B was effective for a higher percentage of patients in both groups, i.
I find it more than a little mind-bending that my heuristics about how to behave on the basis of statistical evidence are obviously not just a little wrong, but utterly, horribly wrong. Or, to put it another way, they have not the first clue about statistics.If there is one type of English essay that holds virtually limitless opportunities for exploration, it is the concept essay.
By culling your knowledge and personal experience and combining it with vivid, colorful examples, you can make a concept essay a uniquely personal and memorable experience. @Suresh – Fascinating idea! No idea if it’s possible, though, the thought never crossed my mind.
I guess I think of causal models as having an inherent directionality, due to the dag structure, while most geometries don’t have the same kind of directionality. Community Conceptual Model Essay Community Conceptual Model Community Conceptual Model Conceptual models are effective guides and tools used for nursing practice.
They merge concepts and ideas providing a framework for how to think or demonstrate the elaborate connections between concepts, structures, or a system. Abstract: The bacterial flagellum is a complex molecular system with multiple components required for functional motility.
Such systems are sometimes proposed as puzzles for evolutionary theory on the assumption that selection would have no function to act on until all components are in place.
Powerful Essays words ( pages) Essay on Organizational Psychology: Psychology And Psychology - Organizational psychology is not actually psychology because instead of focusing on individuals, it focuses more on organizations as a whole.
Conceptual Modification Essay by EssaySwap Contributor, College, Undergraduate, February download word file, 3 pages download word file, 3 pages 0 votes.