c++ - What is the purpose of boost accumulator error_of<mean>? -


the documentation of error_of< mean > feature boost accumulators states calculates error of mean value formula:

sqrt(variance / (count - 1)),

where variance calculated by:

variance = 1/count sum[ (x_i - x_m)^2 ] sum goes on values x_i i=1..count of sample , x_m mean value. gives used formula (for error value):

sqrt(1/ (count(count - 1)) sum[ (x_i - x_m)^2 ] ),

wikipedia states standard deviation, 1 use either uncorrected or corrected sample standard deviation. latter calculated by:

sqrt(1/(count-1) * sum[ (x_i - x_m)^2] )

this 1 use calculate errors of mean values. purpose of error_of< mean >? , error calculated there?

the overall formula of boost.accumulators indeed correct, computed in non-standard fashion.

first, sample variance average of squared deviations

v_sample = sum[ (x_i - x_m)^2] / count s_sample = sqrt[ v_sample ]

but s_sample biased estimater of population standard deviation sigma. unbiased estimator of population standard deviation is

s_pop = s_sample * sqrt[ count / count - 1 ]

second, standard error on mean error have measured mean. can use standard error on mean construct confidence intervals around sample arithmetic mean estimator of population mean mu.

the standard error on mean given ratio of unbiased estimator of population standard deviation divided square root of number of observations

s_mean = s_pop / sqrt[ count ]

boost.accumulator computes s_mean as

s_mean = s_sample / sqrt[count - 1]

but 2 expression equivalent, can readily seen direct substition of relation between s_pop , s_sample.

note: think useful boost.accumulators define these 2 versions of standard deviation.


Comments

Post a Comment

Popular posts from this blog

jquery - How can I dynamically add a browser tab? -

since using iframes house external pages are, accounts "not preferred method" , disallowed sites (flickr, one), want dynamically generate browser tabs. e.g., when user submits form, want dynamically generate tab on browser in response submitted. e.g., might want add new tab url like: http://www.bigsurgarrapata.com/contact how in jquery? you want form target attribute action attribute. http://www.w3schools.com/tags/att_form_target.asp browsers have ultimate control on result of target attribute open new tab value of _blank. <form action="contact_submit.php" target="_blank" method="post">
Read more

keyboard - C++ GetAsyncKeyState alternative -

i using windows.h library's getasynckeystate function define key pushed on keyboard . here program returns int value of pushed key example. #include <iostream> #include <windows.h> using namespace std; int main (){ char i; for(i=8;i<190;i++){ if(getasynckeystate(i)== -32767){ cout<<int (i)<<endl; } } return 0; } but trying make opengl simple game , function appeared slow . there function not need cycle 180 times , if statement . thanks you're trying make opengl game, you're going use glfw. if that's case can away using glfwgetkey() such: if (glfwgetkey(glfw_key_up) == glfw_press) {...} if (glfwgetkey(glfw_key_down) == glfw_press) {...} that method nicely explained in tutorial 6 opengl-tutorial.org . should start first tutorial of beginners tutorials , later intermediate tutorials . if you're going make win32 window can listen wm_keydown or wm_keyup messages , virtua...
Read more

android - java.net.UnknownHostException(Unable to resolve host “URL”: No address associated with hostname) -

i developing app testing asp.net webservice in android.for simple webservice adding 2 numbers used.where numbers passed parameters.the result in dialogue.the webserver works in local. when application runs following result exception.i provided internet permission in manifest. java.net.unknownhostexception(unable resolve host “ http://url.com/ ”: no address associated hostname) my code given below main activity public static string rslt=""; /** called when activity first created. */ @override public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.activity_main); button b1=(button)findviewbyid(r.id.button1); final alertdialog ad=new alertdialog.builder(this).create(); b1.setonclicklistener(new onclicklistener() { @override public void onclick(view arg0) { // todo auto-generated method stub try { ...
Read more