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Basic medical statistics for Clinicians

PROF./ TAREK EMRAN

Professor and Head of Clinical Pathology Department

Damietta Faculty of Medicine- Al-Azhar University

ASSOCIATE ALUMNI OF HARVARD MEDICAL SCHOOL

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How to choose the best statistical test

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P Values

The probability that any observation is due to chance alone assuming that the null hypothesis is true

Typically, an estimate that has a p value of 0.05 or less is considered to be “statistically significant” or unlikely to occur due to chance alone.

The P value used is an arbitrary value

P value of 0.05 equals 1 in 20 chance

P value of 0.01 equals 1 in 100 chance

P value of 0.001 equals 1 in 1000 chance.

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Correlation

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Correlation

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Statistical box plot

Box plots graphically depict numerical data using their descriptive statistics,

0 Mean extreme value , must delete ; * outline value, not delet

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Evaluation of diagnostic performances of markers

AUC equal to 1.0 is characteristic of an ideal test, whereas 0.5 indicates a test without diagnostic value. The nearer a curve shifts to the top left and corner of the graph, the more useful the marker is for

the diagnosis.

Receiver Operating Curve (ROC), Sensitivity , Specificity

Positive predictive value (PPV)

Negative predictive value (NPV)

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Tips and triks in results presentation

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Dr. Tarek Emran