Hello. I don't know if you can help me but I try. I have a collection of objects, we suppose that they are 1000. After some works that I made I divided this collection in some clusters. Suppose to have obtained 50 clusters. For each cluster I found a particular value called Precision, where 0<Precision<1. Taken the firs cluster I want to compare his Precision with the precision of his complement that his obtained by the union of the remainder clusters. After this I want to take the second cluster and make the same thing comparing his precision with the precision of his complement. Take the third cluster and so on. I want to do this for each cluster. I want to use a test that compare the precision obtained for each cluster with the precision of each complement. I want to know if the precision of the singolar clusters are significantly different respect the precision of the complement. I think that I have to make a vector with the precision of the clusters and a vector with the precision of the complement. Maybe I have to find the means of each vector and compare them. But wich is the test that I have to use? Is it a t-student? And wich command I have to use if I want to make this test? -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._
On 05/22/02 21:35, Ambrosini Alessandro wrote:>Hello. I don't know if you can help me but I try. >I have a collection of objects, we suppose that they are 1000. After some >works that I made I divided this collection in some clusters. Suppose to >have obtained 50 clusters. For each cluster I found a particular value >called Precision, where 0<Precision<1. >Taken the firs cluster I want to compare his Precision with the precision of >his complement that his obtained by the union of the remainder clusters.So you want to compare two numbers. Without some estimate of the error of each number, I don't see how you can do this. I am assuming that the "precision of the complement" is one number. [If it is actually 49 numbers, then you can (in principle) use a t test, or a z test, comparing one number to the mean of the 49, if you are willing to use the standard deviation of the 49 to estimate the error of the one (which seems reasonable). But I don't think you mean this, because, if you did, the mean difference between each number and the mean of the 49 others would be zero.]>After this I want to take the second cluster and make the same thing >comparing his precision with the precision of his complement. Take the third >cluster and so on. I want to do this for each cluster. >I want to use a test that compare the precision obtained for each clusterI don't think you mean "each".>with the precision of each complement. I want to know if the precision of >the singolar clusters are significantly different respect the precision of >the complement. I think that I have to make a vector with the precision of >the clusters and a vector with the precision of the complement. Maybe I have >to find the means of each vector and compare them. But wich is the test that >I have to use? Is it a t-student? And wich command I have to use if I want >to make this test?Now it sounds more like you are comparing two numbers for each cluster. Its precision and the precision of its complement. A t test does sound reasonable. But you want the matched-pairs version. So if you have two vectors - clusters and complements - you say t.test(clusters,complements,paired=T) or, equivalently, t.test(clusters-complements) (except that one may be the reverse of the other - I never remember which way the first one goes). See the help for t.test. Jon Baron -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._
Dependence between complements might complicate things, depending on how "precision" is calculated. So will the fact that the clustering rule is presumably a function of the same data you're analyzing. In general you might want to use resampling methods to handle this. It would be hard to recommend anything without more details: how do you calculate precision? How do you arrive at clusters? What is it you're trying to do--what's the big picture? That actually matters as there are many hypotheses of homogeneity one could test... Reid Huntsinger -----Original Message----- From: Ambrosini Alessandro [mailto:klavan at tiscalinet.it] Sent: Wednesday, May 22, 2002 3:36 PM To: R-help Subject: [R] Problem Hello. I don't know if you can help me but I try. I have a collection of objects, we suppose that they are 1000. After some works that I made I divided this collection in some clusters. Suppose to have obtained 50 clusters. For each cluster I found a particular value called Precision, where 0<Precision<1. Taken the firs cluster I want to compare his Precision with the precision of his complement that his obtained by the union of the remainder clusters. After this I want to take the second cluster and make the same thing comparing his precision with the precision of his complement. Take the third cluster and so on. I want to do this for each cluster. I want to use a test that compare the precision obtained for each cluster with the precision of each complement. I want to know if the precision of the singolar clusters are significantly different respect the precision of the complement. I think that I have to make a vector with the precision of the clusters and a vector with the precision of the complement. Maybe I have to find the means of each vector and compare them. But wich is the test that I have to use? Is it a t-student? And wich command I have to use if I want to make this test? -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-. -.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._. _._ ------------------------------------------------------------------------------ Notice: This e-mail message, together with any attachments, contains information of Merck & Co., Inc. (Whitehouse Station, New Jersey, USA) that may be confidential, proprietary copyrighted and/or legally privileged, and is intended solely for the use of the individual or entity named in this message. If you are not the intended recipient, and have received this message in error, please immediately return this by e-mail and then delete it. ============================================================================= -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._