
 
 Biostatistics High Yield Notes 

Ztest : A Brief Overview
by  9517 reads, based on 7 votes
In some situations the sequence of steps used in ttest can be done using zscores instead of tscores. Then such a test is called ztest.
Use: ztest is/can be used in place of ttest when
• The population standard deviation is known which allows the standard error, rather than the estimated SE to be found
• The sample is sufficiently large (n > 200) for the SD to provide a reliable estimate of SE....
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All the Biostatistics notes you will need for a quick revision
by willpower  29070 reads, based on 59 votes
BIOSTATISTICS NOTES
POPULATION: Universe of all units being studied.
If we want to study lung cancer among Indians, then the study population will be all Indians.
If we want to study lung cancer among Indian women, then the population will be all
Indian women.
SAMPLE: Subset of the population
RANDOM SAMPLE: Each member of the population has an EQUAL CHANCE of being chosen for the sample ...
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Principles of Diagnostic Tests
by akil  5392 reads, based on 4 votes
A summary of diagnostic tests principles!
Test Positive or Negative
The definition of normal for continuous variables is a statistical determination
At what point "abnormal" becomes an illness or disease is a judgment based upon the desire to identify those with disease (true positives), but not include a significant portion of patients without the disease (false positives). Furthermore, most tests are not positive in all the patients with a given disease, so there will be patients with the disease who are missed by the test (false negatives). Finally, we want to be sure that a very high proportion of patients who don't have the disease, have a negative test (true negatives).
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