Statistics – Tests of significance

Q) To Study the effect of an antiviral  drug, we note down the initial viral load and then after  a month repeat viral load. What is the   the most appropriate statistical test of significance to test the change in viral load

(a) Paired t-test
(b) Unpaired or independent t-test
(c) Analysis of variance
(d) Chi-square test

Ans a) Paired t test

paired t test is used When comparing the same person results after giving a drug or doing a surgery or any intervention

A paired t-test is used when we are interested in the difference between two variables for the same subject. Often the two variables are separated by time

Unpaired t test

The unpaired two-samples t-test is used to compare the mean of two independent groups.

For example, suppose that we have measured the weight of 100 individuals: 50 women (group A) and 50 men (group B). We want to know if the mean weight of women  is significantly different from that of men In this case, we have two unrelated (i.e., independent or unpaired) groups of samples. Therefore, it’s possible to use an independent t-test to evaluate whether the means are different.

Chi-square test

The basic idea behind the test is to compare the observed values in your data to the expected values that you would see if the null hypothesis is true.

To determine whether the association between two qualitative variables is statistically significant

Analysis of Variance ANOVA example

A group of psychiatric patients are trying three different therapies: counseling, medication and biofeedback. You want to see if one therapy is better than the others.


EHPVO with Portal Hypertension

Q) An young male with cholangitis, EHPVO + Portal Biliopathy was drained with a plastic biliary stent next step?

a) Repeat biliary Stenting every 3 months then followed up

b) Replace plastic to bare metal stent

c) Prepare for Lineorenal shunt surgery

d) Do MRCP and proceed accordingly

Points  about Portal Biliopathy

Portal biliopathy (PB) is a clinical condition defined as the presence of abnormalities in the biliary tree (including biliary tree and gallbladder) in patients with non-cirrhotic/non-neoplastic extrahepatic portal vein obstruction (EHPVO) and portal cavernoma.

The spectrum of biliary abnormalities include both  intra- and extra-hepatic biliary stenosis (single or multiple)

With or without consensual above dilation

Bile duct wall irregularity or thickening

Bile duct angulation

Varicose veins located at the ductular walls and gallbladder