In my stats class, we have a formulat for a single sample t-test which is given as: t = (Xbar - mu) / sigma where: Xbar is the sample mean, mu is the population mean, and sigma is the population StdDev. It goes on to say that if sigma is unknown, the StdErr may be used which is: sigma(Xbar) = S / Sqrt(N) where: S is the sample StdDev and N is the sample size. What if the population mean is unknown also? How can I calculate the t-score? My sample size is 10.

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5/10/2006 1:45:35 PM

seven_percent wrote: > In my stats class, we have a formulat for a single sample t-test which > is given as: > > t = (Xbar - mu) / sigma > > where: Xbar is the sample mean, mu is the population mean, and sigma > is the population StdDev. This is not correct. t = (Xbar-mu)/SE_Xbar where SE_Xbar = S/SQRT(n). > > It goes on to say that if sigma is unknown, the StdErr may be used > which is: > > sigma(Xbar) = S / Sqrt(N) > > where: S is the sample StdDev and N is the sample size. I think the distinction you are trying to make is between knowing and not knowing the population standard deviation, sigma. If sigma is known: z = (Xbar - mu)/SE where SE = sigma/SQRT(n) If sigma is NOT known, you use the sample standard deviation S as an estimate of sigma: t = (Xbar - mu)/SE where SE = S/SQRT(n) n = sample size S = sample standard deviation (with division by n-1) Xbar = sample mean mu = population mean given some null hypothesis df for the t-ratio = n-1 > What if the population mean is unknown also? How can I calculate the > t-score? My sample size is 10. The value of mu is specified in some null hypothesis you wish to test. So the only way it can be unknown is if you have no null hypothesis. -- Bruce Weaver bweaver@lakeheadu.ca www.angelfire.com/wv/bwhomedir

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5/10/2006 2:44:04 PM

I guess my teacher's notes are incorrect then. I am trying to apply the concepts from the lesson to determine if $465,000 is a reasonable amount to ask for our house. My "research hypothesis" in this case is "I am 95% certain that $465,000 is a reasonable amount to ask for our house." I have 10 home prices for the same # of bedrooms, bathrooms, sqft, and lot size. I calculated the median, mode, midpoint, mean, and standard deviation. I began to use a normal distribution and thought that I could see what the z-score would be for $465,000. Then I remembered that with sample sizes < 1000, you are supposed to use t-scores instead. That's where I ran into problems. Any ideas for this problem?

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5/10/2006 3:17:15 PM

Hi! I need help of those who are good at stat.analysis to perform the following in SPSS: I have, in my analysis, identified 4 groups of consumers. Now I would like to compare them on several criteria. The thing is, criteria are a set of many items which by factor analysis were reduced to 6 factors. I don't know if for comparing groups I should use a) factor scores (the most popular method, from what I've read, is regression-based scores created by spss during factor analysis) or b) create mean scores from each several items belonging to 1 factor (and use z-scores for compari...

I know how to do this manually and I created an Excel spreadsheet using a lookup table. Is there a way to have SPSS spit-out the percentile ranking given the other three data? I don't understand what you mean by "the other 3 data". The easiest way to get percentiles is something like. RANK variables= raw1 raw2 raw3 /percent /into pctl_raw1 pctl_raw2 pctl_raw3. Art Art@DrKendall.org Social Research Consultants seven_percent wrote: > I know how to do this manually and I created an Excel spreadsheet using > a lookup table. Is there a way to have SPSS spit-out the percentile > ranking given the other three data? > "Given Mean/Std Dev/Score. . ." those three data. In other words, I don't have a data set. I merely know the Mean, Std Dev, and a Score. I can calculate a Percentile score manually by calculating the z Score and looking it up. I can do the same thing in Excel, with a few formulas and a lookup table. How do I acheive the same thing in SPSS using the most simple and non-convoluted manner? seven_percent wrote: > "Given Mean/Std Dev/Score. . ." those three data. In other words, I > don't have a data set. I merely know the Mean, Std Dev, and a Score. > I can calculate a Percentile score manually by calculating the z Score > and looking it up. I can do the same thing in Excel, with a few > formulas and a lookup table. How do I acheive the same th...

I have a strange Perl problem I don't understand. I've written the following program to scan different disks on a Windows server to look for directory files. Works fine until it gets to 'e:' when I get this warning: Can't stat e:: Unknown file or directory (If I don't have the "use warnings" in the code I get no message.) There are folders and files on e:. I don't understand what the problem is but I suspect there's some kind of syntax issue. use File::Find; use warnings; @disks = ('h:','g:','f:','e:','d:'...

I often see it written here that the declaration T t = a; (where 'a' is not of type T) calls the copy-constructor and is exactly equivalent to T t(( T(a) )); However the following code gives me a compiler error: #include <string> struct M { M(std::string const &s); }; int main() { M a ("Hello"); M b = M("Hello"); M c ( M("Hello") ); M d = "Hello"; return 0; } m.cc:13: error: conversion from `const char[6]' to non-scalar type `M' requested The error is one the "M d&...

I have a strange Perl problem I don't understand. I've written the following program to scan different disks on a Windows server to look for directory files. Works fine until it gets to 'e:' when I get this warning: Can't stat e:: Unknown file or directory (If I don't have the "use warnings" in the code I get no message.) There are folders and files on e:. I don't understand what the problem is but I suspect there's some kind of syntax issue. Here's the code. When I run it with this list of disks: @disks = ('h:','g:','f...

I am trying to assess the level of agreement between two raters who rated items as either Yes or No. This calls for Kappa. But if one rater rated all items the same, SPSS sees this as a constant and doesn't calculate Kappa. For example, SPSS will not calculate Kappa for the following data, because Rater 2 rated everything a Yes. Rater1 Rater2 Item1 Y Y Item2 N Y Item3 Y Y Item4 Y Y Item5 N Y SPSS completes the crosstab (which shows that the raters agreed 60% of the time), but as for Kappa, it returns this note: "No measures of association are computed for the crosstabulation of VARIABLE1 and VARIABLE2. At least one variable in each 2-way table upon which measures of association are computed is a constant." Is there anywhere to get around this? I can calculate Kappa by hand with the above data; why doesn't SPSS? Thanks. Kurt Kurt wrote: > I am trying to assess the level of agreement between two raters who > rated items as either Yes or No. This calls for Kappa. But if one > rater rated all items the same, SPSS sees this as a constant and > doesn't calculate Kappa. > > For example, SPSS will not calculate Kappa for the following data, > because Rater 2 rated everything a Yes. > > Rater1 Rater2 > Item1 Y Y > Item2 N Y > Item3 Y ...

A few weeks ago, someone pointed out that you can use the /SAVE option of DESCRIPTIVES to save z-scores to your working data file. It just dawned on me today that the SD SPSS calculates is the sample SD, with n-1 in the denominator. I suspected, therefore, that the z-scores generated by DESCRIPTIVES would be calculated as follows: z = (X - Xbar)/s where Xbar = sample mean, and s = sample SD (with n-1 in denominator). I checked, and this is indeed how SPSS computes z-scores. But many textbooks, it seems show the formula for z as: z = (X-mu)/sigma where mu = po...

Hi, I'm attempting to use Mathematica to calculate a mean-position eigenfunction of the Dirac equation. To do so I need to evaluate Fourier transforms (from k-space to r-space) of wavefunctions dependent on: ( (1 + k^2 + (1 + k^2)^(1/2) )^(-1/2) where k is in units of the Compton wavevector. Cell expression: Cell[BoxData[ FractionBox["1", SqrtBox[ RowBox[{"1", "+", SuperscriptBox["k", "2"], "+", SqrtBox[ RowBox[{"1", "+", Supe...

Hello. I am sampling the current and voltage simultaniously. Right now I am calculating reactive power in two ways: 1). delay the current samples by a quarter of a period and then multiplying: Q=i(n+pi/2)*u(n) 2). or using the following procedure: P=1/(num. samples)*sum( i(n)*u(n) ) -> active power S=Irms*Urms -> apparent power Q=sqrt(P^2 - Q^2) -> reactive power Unfortunatelly neither give me good results. Is there a nother way to compute reactive power? I can't use any complicated FFt algorithm as the processor isn't very browny. Let...

http://www.ut2341.com/UT3SystemScore/ Nothing to d/l, just input your specs. I get 19.8! rms "rms" <rsquires@REMOVEflashMOO.net> wrote in message news:BPNPi.58770$YL5.16841@newssvr29.news.prodigy.net... > http://www.ut2341.com/UT3SystemScore/ > > Nothing to d/l, just input your specs. I get 19.8! > > rms > > I got 22.7. Then I entered my *real* specs and got 16.17. /cries softly "Schrodinger" <no@way.com> writes: > "rms" <rsquires@REMOVEflashMOO.net> wrote in message > news:BPNPi.58770$YL5.16841@newss...

Hi, This might sound stupid, but I really hope someone could clear these terms for me. Thank you. awa wrote: > Hi, > > This might sound stupid, but I really hope someone could clear these > terms for me. A Soft CPU is one that can be field reconfigured, and is not hardwired in silicon. Most common form are implemented in FPGAs, so look for PicoBlaze, PacoBlaze, MicroBlaze, NIOS, NIOS II, Mico8, Mico32, on the net, for examples. Just to confuse you more, some of these SoftCPUs are available under license, to be used to build hard-Wired CPUs :) -jg Hi Jim, Oh no. Another t...

http://macdailynews.com/index.php/weblog/comments/17694/ "While describing Apple as a 'great company,' Mr Seidenberg highlights its small market share of global handset sales. He scoffs at suggestions that the iPhone is about to become a mass-market handset because Apple has accepted mobile operators' pleas to subsidise it," Parker and Edgecliffe-Johnson report. "As handsets become banking tools and games controllers, he argues, mobile operators can up-end other companies' business models. 'It's very cool. And Steve Jobs eventually will get old . ...

Hoping someone out there can help me with a manual factor score calculation, that in the end must be exaclty the same as the factor scores which a Factor Analysis spits out in SPSS. Initially I ran a factor analysis on standardized variables in SPSS. The FACTOR command automatically creates factor scores in my data FAC_1, FAC_2, and so on. Then I tried to re-create the scores manually using the Factor Score Coefficient Matrix. I multiplied the values of the standardized variables by the Factor Score Coefficient Matrix (I had to flip the matrix in order to run the MATRIX command properly), and that's how I got my manually calculated factor scores. However when I compare the factor scores from SPSS to the ones I've created, they are close but not exactly the same. It's not a huge difference, but big enough so that my model is not longer scored the same as it was built. What is the proper way to manually create factor scores to match up with SPSS generated factor scores? Thanks in advance. ------------------------------------------------------------ I read this online - not sure if I answered my own question with this, but I hope I can still manually create the same factor scores as SPSS. "It is sufficient to note here that factor scores calculated by computer packages such as SPSS are based on approximations, and the validity of these scores may vary from factor to factor. It has been shown (Guttman, 1955; See also Mather, 1...

<p> I think everyone knows the shoes is apart of our dressing, it can influence our appearance also. Therefore, choose the most suitable shoes for you are very important, than it is obvious that the Nike shoes is the most wonderful shoes for your choice. The Nike Air Max Shoes are new productions that are <a title="Air Force One" href="http://www.nike-airmax-seller.com/">Air Force One</a>pushed out in these years. They are well-sale that so many people affirm them. Here, let Kitty take you to look at some features of the Nike Air Max shoes.</p> <p...

Hi! I have a time series 2D matrix with columns for month, day, hour and an observation variable. Some days have more observations than others. Can someone point me in the right direction of how to f.ex. calculate a daily mean of the observations, so that each day in each month have one mean observation-value instead of several individual observations? Anders On 6 Feb, 10:52, Anders <amf...@gmail.com> wrote: > Hi! > I have a time series 2D matrix with columns for month, day, hour and an observation variable. Some days have more observations than others. > > Can someone po...

Hi Im new to using ML and I'm trying to calculate the mean. I got as far as fun sum nil = 0.0 | sum (h::t) = h + sum(t); fun length nil = 0.0| length (h::t) = 1.0 + length(t); fun mean nil= 0.0 | mean(h::t) = sum (h::t) / length (h::t); But this only works for real numbers, I want it to be able to work for both, int and real. Do I have to use the "ceiling" conversion?? Many Thanks Simon Pole <simon_pole@ntlworld.com> wrote: > I got as far as > fun sum nil = 0.0 | sum (h::t) = h + sum(t); > fun length nil = 0.0| length (h::t) = 1.0 +...

Hi, i have a lot of data and want to calc a mean for every 60th number. So mean for 1:60 and then 61:120, 121:180 and so on. What is the easiest way? thx Martin "Martin " <martin.drougge.4639@student.uu.se> wrote in message <l3e1ua$hk8$1@newscl01ah.mathworks.com>... > Hi, i have a lot of data and want to calc a mean for every 60th number. > So mean for 1:60 and then 61:120, 121:180 and so on. > What is the easiest way? What if you were to reshape the vector into an array? Suppose an array with 60 rows, and as many columns as is needed. No...

How should I do if I want to calculate x - mean(x)? Thanks. Regards, Jing "Jim" Quan Dept of Info and Decision Sciences Salisbury University I don't understand the problem! how about m=x-mean(x); ??? Regards, Gerhard On Mon, 9 Oct 2006 16:47:07 -0400, Jing Quan <JXQUAN@SALISBURY.EDU> wrote: >How should I do if I want to calculate x - mean(x)? Thanks. > > >Regards, > >Jing "Jim" Quan >Dept of Info and Decision Sciences >Salisbury University On Mon, 9 Oct 2006, Jing Quan wrote: > How should I do if I want to calculate x - mea...

Hi at all, first, sorry for the bad english... i have to calculate the mean of an image without using the command "mean". with mean i resolve in this way: [code]a=imread('x.JPG'); [M,N]=size(a); %mask 5x5 for i=1:M-4 for j=1:N-4 c = a(i : i+4 , j : j+4); media5(i,j)=mean( c ( : ) ); end; end;[/code] the teacher says that shoul be used more for-cycle, but i have no idea about how implement it. Thanks in advance ...

Is it possible to find mean for each pixel in an image using 8 neighbour connectivity? "Rajeshkumar " <mailtorajeshmit@gmail.com> wrote in message <ik3i1i$ipu$1@fred.mathworks.com>... > Is it possible to find mean for each pixel in an image using 8 neighbour connectivity? doc conv2 On Feb 23, 1:01=A0pm, "Rajeshkumar " <mailtorajesh...@gmail.com> wrote: > Is it possible to find mean for each pixel in an image using 8 neighbour = connectivity? % Read in monochrome uint8 image. grayImage =3D imread(fullFileName); % Get average in 3x3 sl...

Hey,check out http://www.2getwork.com for any one looking for a job.It helped me.. v9ZCK ...

Hi I´m about learning C/C++ and after covering the language basics I´m now heading for my first "real" application where I need to use the POSIX stuff for directory operations. Here´s my problem: The following code compiles and runs as it should inside a linux g++ environment using code::blocks IDE. But when I drop the "struct" prefix from line 12 "struct stat st;" It doesn´t compile any more and it says: |12|error: expected `;' before ‘st’ |12|warning: statement is a reference, not call, to function ‘stat’ |12|warning: statement has no...

Hi all, [1] The distortion score of optimal path got from DTW should be converted to likelihood score for combining different systems. So how can we convert? [2] Also how can we decide the optimal threshold for calculating FALSE ALARMS and MISSED DETECTIONS? Another question: Does any body know how to evaluate Mediaeval spoken web search task 2013? Could you please explain? Thanks in advance. ...

How long has it been since the big takeover, two, three weeks? Already, and the last two notes to support have not been answered, not even the automatic ones. fugitive wrote: > How long has it been since the big takeover, two, three weeks? > Already, and the last two notes to support have not been answered, not > even the automatic ones. Probably a major layoff at Jasc/Corel. :-) Uni "Uni" <no.email@no.email.invalid> wrote in message news:41C78140.3080705@no.email.invalid... > > Probably a major layoff at Jasc/Corel. They should call it Jorel. On Mon, ...

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