Monthly Archives: July 2009

Two sample Z-test

July 22, 2009
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Two sample Z-test

Comparison of the means of two independent groups of samples, taken from two populations with known variance.Is asked to compare the average heights of two groups. The first group (A) consists of individuals of Italian nationality (the variance of the ...

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Massively parallel database for analytics

July 22, 2009
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Massively parallel database for analytics

This is by far the best description of why traditional parallel databases (like Teradata, Greenplum et al.) is a evolutionary dead end. But much more than a theoretical discussion, they have built a solution which they call HadoopDB. It is based on Hadoop, PostgreSQL, and Hive and is completely Open Source. Alternative, column-based, backends to PostgreSQL...

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Massively parallel database for analytics

July 22, 2009
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Massively parallel database for analytics

This is by far the best description of why traditional parallel databases (like Teradata, Greenplum et al.) is a evolutionary dead end. But much more than a theoretical discussion, they have built a solution which they call HadoopDB. It is based on Hadoop, PostgreSQL, and Hive and is completely Open Source. Alternative, column-based, backends to PostgreSQL...

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One sample Z-test

July 21, 2009
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One sample Z-test

Comparison of the sample mean with know population mean and standard deviation.Suppose that 10 volunteers have done an intelligence test; here are the results obtained. The mean obtained at the same test, from the entire population is 75. You want to c...

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RGG#155, 156 and 157

July 21, 2009
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RGG#155, 156 and 157

I pushed 3 more graphics from Biecek Przemyslaw to the graphics galleryA list of popular names for colors from packages RColorBrewer, colorRamps, grDevicesA set of examples of few graphical low-level parameters lend, ljoin, xpd, adj, lege...

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Score with scoring rules

July 21, 2009
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Score with scoring rules

INCENTIVES TO STATE PROBABILITIES OF BELIEF TRUTHFULLY We have all been there. You are running an experiment in which you would like participants to tell you what they believe. In particular, you’d like them to tell you what they believe to be the probability that an event will occur. Normally, you would ask them. But

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Geometric and harmonic means in R

July 20, 2009
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Geometric and harmonic means in R

Compute the geometric mean and harmonic mean in R of this sequence.10, 2, 19, 24, 6, 23, 47, 24, 54, 77These features are not present in the standard package of R, although they are easily available in some packets. However, it is easy to calculate the...

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Adding a legend to a plot

July 20, 2009
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Adding a legend to a plot

It's pretty easy!plot (c(1968,2010),c(0,10),type="n", # sets the x and y axes scales xlab="Year",ylab="Expenditures/GDP (%)") # adds titles to the axes lines(year,defense,col="red",lwd=2.5) # adds a line for defense expenditures lines(year,health,col="...

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Adding a legend to a plot

July 20, 2009
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Adding a legend to a plot

It's pretty easy!plot (c(1968,2010),c(0,10),type="n", # sets the x and y axes scales xlab="Year",ylab="Expenditures/GDP (%)") # adds titles to the axes lines(year,defense,col="red",lwd=2.5) # adds a line for defense expenditures lines(year,health,col="...

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Example 7.6: Find Amazon sales rank for a book

July 20, 2009
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Example 7.6: Find Amazon sales rank for a book

In honor of Amazon's official release date for the book, we offer this blog entry.Both SAS and R can be used to find the Amazon Sales Rank for a book by downloading the desired web page and ferreting out the appropriate line. This code is likely to br...

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