Hotelling's T-squared distribution: Difference between revisions

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"Why does my computer keep freezing up?" I was asked by a lot of persons the cause of their pc freeze difficulties. And I am fed up with spending much time in answering the query time plus time again. This article is to tell you the real cause of the PC Freezes.<br><br>Another answer is to supply the computer system with a fresh msvcr71 file. Frequently, once the file has been corrupted or damaged, it may no longer be able to function like it did before thus it's just all-natural to substitute the file. Simply download another msvcr71.dll file within the web. Frequently, the file will come inside a zip formatting. Extract the files within the zip folder and destination them accordingly in this location: C:\Windows\System32. Afterward, re-register the file. Click Start and then choose Run. When the Run window appears, kind "cmd". Press Enter plus then type "regsvr32 -u msvcr71.dll" followed by "regsvr32 msvcr71.dll". Press Enter again and the file must be registered accordingly.<br><br>The 'registry' is a central database which stores info, settings plus choices for your computer. It's really the many prevalent reason why XP runs slow and when you fix this issue, we could create a computer run a lot faster. The problem is the fact that the 'registry' shops a lot of settings plus details regarding your PC... and considering Windows must utilize a lot of of these settings, any corrupted or damaged ones may straight affect the speed of the system.<br><br>The issue with almost all of the people is the fact that they never like to invest funds. In the cracked variation 1 refuses to have to pay anything and could download it from web rather easily. It is easy to install because well. But, the issue comes when it really is unable to identify all possible viruses, spyware plus malware in the system. This really is because it is very obsolete in nature plus does not receive any regular changes within the website downloaded. Thus, your system is accessible to difficulties like hacking.<br><br>Another well-known cause of PC slow down is a corrupt registry. The registry is a important component of computers running on Windows platform. When this gets corrupted a PC will slowdown, or worse, not begin at all. Fixing the registry is easy with the use of a system and [http://bestregistrycleanerfix.com/tune-up-utilities tuneup utilities 2014].<br><br>The software finds these issues and takes care of them inside the shortest time possible. Your difficult drive might also result problems sometimes, incredibly when you have 1 that is virtually maxed. When a commence the machine, the are so many booting processes involved and having an almost full storage space refuses to assist a bit. You will always have a slow PC because there are a lot of points inside the difficult disk being processed at the same time. The best method to solve this issue is to upgrade. This can allow the PC some time to breathing plus functioning faster instantaneously.<br><br>It is important which you remove obsolete registry entries from the system regularly, if you need the program to run faster, which is. If you don't keep a registry clean, a time comes when the program can stop working completely. Next, a just way will be to reformat a hard drive and start over!<br><br>There are many businesses that provide the service of troubleshooting the PC every time we call them, all you have to do is signal up with them and for a tiny fee, you have a machine constantly functioning effectively plus serve we better.
{{Distinguish|Likelihood-ratio test}}
 
In [[evidence-based medicine]], '''likelihood ratios''' are used for assessing the value of performing a diagnostic test. They use the [[sensitivity and specificity]] of the test to determine whether a test result usefully changes the probability that a condition (such as a disease state) exists.
 
==Calculation==
 
Two versions of the likelihood ratio exist, one for positive and one for negative test results.  
Respectively, they are known as the ''likelihood ratio positive'' (LR+) and ''likelihood ratio negative'' (LR–). 
 
The likelihood ratio positive is calculated as
 
:<math> LR+ = \frac{\text{sensitivity}}{1 - \text{specificity}} </math>
 
which is equivalent to
 
:<math> LR+ = \frac{\Pr({T+}|D+)}{\Pr({T+}|D-)} </math>
 
or "the probability of a person who has the disease testing positive divided by the probability of a person who does not have the disease testing positive."
Here "T+" or "T&minus;" denote that the result of the test is positive or negative, respectively. Likewise, "D+" or "D&minus;" denote that the disease is present or absent, respectively. So "true positives" are those that test positive (T+) and have the disease (D+), and "false positives" are those that test positive (T+) but do not have the disease (D&minus;).
 
The likelihood ratio negative is calculated as<ref name=altman>{{cite book |author=Gardner, M.; Altman, Douglas G. |title=Statistics with confidence: confidence intervals and statistical guidelines |publisher=BMJ Books |location=London |year=2000 |pages= |isbn=0-7279-1375-1 |oclc= |doi= |accessdate=}}</ref>
 
:<math> LR- = \frac{1 - \text{sensitivity}}{\text{specificity}} </math>
 
which is equivalent to<ref name=altman/>
 
:<math> LR- = \frac{\Pr({T-}|D+)}{\Pr({T-}|D-)} </math>
 
or "the probability of a person who has the disease testing negative divided by the probability of a person who does not have the disease testing negative." 
 
The [[pretest odds]] of a particular diagnosis, multiplied by the likelihood ratio, determines the [[post-test odds]]. This calculation is based on [[Bayes' theorem]]. (Note that odds can be calculated from, and then converted to, [[probability]].)
 
==Application to medicine==
A likelihood ratio of greater than 1 indicates the test result is associated with the disease. A likelihood ratio less than 1 indicates that the result is associated with absence of the disease.
Tests where the likelihood ratios lie close to 1 have little practical significance as the post-test probability (odds) is little different from the pre-test probability. In summary, the pre-test probability refers to the chance that an individual has a disorder or condition prior to the use of a diagnostic test. It allows the clinician to better interpret the results of the diagnostic test and helps to predict the likelihood of a true positive (T+) result.<ref>{{cite journal | doi = 10.1001/jama.247.18.2543 | author = Harrell F, Califf R, Pryor D, Lee K, Rosati R | year = 1982 | title = Evaluating the Yield of Medical Tests | url = | journal = JAMA | volume = 247 | issue = 18| pages = 2543–2546 | pmid = 7069920 }}</ref>
 
Research suggests that physicians rarely make these calculations in practice, however,<ref name="pmid9576412">{{cite journal |author=Reid MC, Lane DA, Feinstein AR |title=Academic calculations versus clinical judgments: practicing physicians’ use of quantitative measures of test accuracy |journal=Am. J. Med. |volume=104 |issue=4 |pages=374–80 |year=1998 |pmid=9576412| doi = 10.1016/S0002-9343(98)00054-0}}</ref> and when they do, they often make errors.<ref name="pmid11934776">{{cite journal |author=Steurer J, Fischer JE, Bachmann LM, Koller M, ter Riet G |title=Communicating accuracy of tests to general practitioners: a controlled study |journal=BMJ |volume=324 |issue=7341 |pages=824–6 |year=2002 |pmid=11934776 |pmc=100792| doi = 10.1136/bmj.324.7341.824}}</ref> A [[randomized controlled trial]] compared how well physicians interpreted diagnostic tests that were presented as either [[sensitivity (tests)|sensitivity]] and [[specificity (tests)|specificity]], a likelihood ratio, or an inexact graphic of the likelihood ratio, found no difference between the three modes in interpretation of test results.<ref name="pmid16061916">{{cite journal |author=Puhan MA, Steurer J, Bachmann LM, ter Riet G |title=A randomized trial of ways to describe test accuracy: the effect on physicians' post-test probability estimates |journal=Ann. Intern. Med. |volume=143 |issue=3 |pages=184–9 |year=2005 |pmid=16061916 |doi=}}</ref>
 
==Example==
 
A medical example is the likelihood that a given test result would be expected in a patient with a certain disorder compared to the likelihood that same result would occur in a patient without the target disorder.
 
Some sources distinguish between LR+ and LR&minus;.<ref name="urlLikelihood ratios">{{cite web |url=http://www.poems.msu.edu/InfoMastery/Diagnosis/likelihood_ratios.htm |title=Likelihood ratios |work= |accessdate=2009-04-04}}</ref> A worked example is shown below.
{{SensSpecPPVNPV}}
 
[[Confidence intervals]] for all the predictive parameters involved can be calculated, giving the range of values within which the true value lies at a given confidence  level (e.g. 95%).<ref>[http://www.medcalc.org/calc/diagnostic_test.php Online calculator of confidence intervals for predictive parameters]</ref>
 
==Estimation of pre- and post-test probability==
{{Further|Pre- and post-test probability}}
The likelihood ratio of a test provides a way to estimate the [[pre- and post-test probabilities]] of having a condition.
 
With ''pre-test probability'' and ''likelihood ratio'' given, then, the ''post-test probabilities'' can be calculated by the following three steps:<ref>[http://www.cebm.net/index.aspx?o=1043 Likelihood Ratios], from CEBM (Centre for Evidence-Based Medicine). Page last edited: 1 February 2009</ref>
 
*Pretest odds = (Pretest probability / (1 - Pretest probability)
*Posttest odds = Pretest odds * Likelihood ratio
In equation above, ''positive post-test probability'' is calculated using the ''likelihood ratio positive'', and the ''negative post-test probability'' is calculated using the ''likelihood ratio negative''.
 
*Posttest probability = Posttest odds / (Posttest odds + 1)
 
In fact, ''post-test probability'', as estimated from the ''likelihood ratio'' and ''pre-test probability'', is generally more accurate than if estimated from the ''positive predictive value'' of the test, if the tested individual has a different ''pre-test probability'' than what is the ''prevalence'' of that condition in the population.
 
===Example===
Taking the medical example from above (20 true positives, 10 false negatives, and 2030 total patients), the ''positive pre-test probability'' is calculated as:
 
*Pretest probability = (20 + 10) / 2030 = 0.0148
*Pretest odds = 0.0148 / (1 - 0.0148) =0.015
*Posttest odds = 0.015 * 7.4 = 0.111
*Posttest probability = 0.111 / (0.111 + 1) =0.1 or 10%
 
As demonstrated, the ''positive post-test probability'' is numerically equal to the ''positive predictive value''; the ''negative post-test probability'' is numerically equal to (1 - ''negative predictive value'').
 
==References==
<references/>
 
{{Medical research studies}}
 
[[Category:Medical statistics]]
[[Category:Evidence-based medicine]]
[[Category:Summary statistics for contingency tables]]

Latest revision as of 23:31, 19 September 2014

"Why does my computer keep freezing up?" I was asked by a lot of persons the cause of their pc freeze difficulties. And I am fed up with spending much time in answering the query time plus time again. This article is to tell you the real cause of the PC Freezes.

Another answer is to supply the computer system with a fresh msvcr71 file. Frequently, once the file has been corrupted or damaged, it may no longer be able to function like it did before thus it's just all-natural to substitute the file. Simply download another msvcr71.dll file within the web. Frequently, the file will come inside a zip formatting. Extract the files within the zip folder and destination them accordingly in this location: C:\Windows\System32. Afterward, re-register the file. Click Start and then choose Run. When the Run window appears, kind "cmd". Press Enter plus then type "regsvr32 -u msvcr71.dll" followed by "regsvr32 msvcr71.dll". Press Enter again and the file must be registered accordingly.

The 'registry' is a central database which stores info, settings plus choices for your computer. It's really the many prevalent reason why XP runs slow and when you fix this issue, we could create a computer run a lot faster. The problem is the fact that the 'registry' shops a lot of settings plus details regarding your PC... and considering Windows must utilize a lot of of these settings, any corrupted or damaged ones may straight affect the speed of the system.

The issue with almost all of the people is the fact that they never like to invest funds. In the cracked variation 1 refuses to have to pay anything and could download it from web rather easily. It is easy to install because well. But, the issue comes when it really is unable to identify all possible viruses, spyware plus malware in the system. This really is because it is very obsolete in nature plus does not receive any regular changes within the website downloaded. Thus, your system is accessible to difficulties like hacking.

Another well-known cause of PC slow down is a corrupt registry. The registry is a important component of computers running on Windows platform. When this gets corrupted a PC will slowdown, or worse, not begin at all. Fixing the registry is easy with the use of a system and tuneup utilities 2014.

The software finds these issues and takes care of them inside the shortest time possible. Your difficult drive might also result problems sometimes, incredibly when you have 1 that is virtually maxed. When a commence the machine, the are so many booting processes involved and having an almost full storage space refuses to assist a bit. You will always have a slow PC because there are a lot of points inside the difficult disk being processed at the same time. The best method to solve this issue is to upgrade. This can allow the PC some time to breathing plus functioning faster instantaneously.

It is important which you remove obsolete registry entries from the system regularly, if you need the program to run faster, which is. If you don't keep a registry clean, a time comes when the program can stop working completely. Next, a just way will be to reformat a hard drive and start over!

There are many businesses that provide the service of troubleshooting the PC every time we call them, all you have to do is signal up with them and for a tiny fee, you have a machine constantly functioning effectively plus serve we better.

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