MCQsOnline - Online Collection of MCQs of Medical PG Entrance Exams.

MCQ stands for Multiple Choice Questions sometimes called as Objective type questions. Here we discuss the Old Question Papers, High Yield Points and Strategies with respect to the Indian Medical Post Graduate PG Entrance Exams like AIIMS,AIPG, JIPMER, CMC Vellore, PGI Chandigarh, UPSC, TNPSC, State PG Exams like Tamil Nadu PG (TN PG), Delhi PG, UPPG, Tamilnadu PG (TNPG), Karnataka PG, MAHE, COMED-K etc.

Target PG

PG Preparation

Related Portals

Search This Site

If you cannot locate what you want to find, please search using the box given below

Tuesday, March 11, 2008

Purpose of double blinding in clinical trials

051. The purpose of double blinding in clinical trials is to:

1. Achieve comparability between study and control groups

2. Avoid observer bias

3. Avoid subject bias

4. Avoid observer and subject bias

Answer

4. Avoid observer and subject bias

Reference

Park 18th Edition Page 77

Quality

Reader

Status

Repeat

QTDF

Park

Discussion

Bias may arise from errors of assessment of the outcome due to human element. These may be from three soruces – the participant, the observer and the interpretor. Randomisation cannot guard against these sorts of bias, nor the size of the sample. In order to reduce these problems, a technique known as “blinding” is adopted, which will ensure that the outcome is assessed objectively

Explanation

Blinding can be done is three ways

  1. Single Blinding -
  2. Double Blinding
  3. Triple Blinding

Comments

Trials can be Open trial or Blind Trial

Open trial: In an open trial, the researcher knows the full details of the treatment and so does the patient. These trials are open to challenge for bias, and they do nothing to reduce the placebo effect. However, sometimes they are unavoidable, particularly in relation to surgical techniques, where it may not be possible or ethical to hide from the patient which treatment he or she received.

Open Trial

Participant aware

Possibility of Subject Bias

Single Blind Trial

Participant not aware whether he belongs to the study group or control group

Eliminates Subject Bias, but possibility of Observer Bias and Evaluation Bias

Double Blind Trial

Participant (patient) is not aware whether he belongs to the study group or control group

And

Observer (doctor) also is not aware whether he belongs to the study group or control group

And

Eliminates Subject Bias and also observer Bias, but possibility of Evaluation Bias

Triple Blind Trial

Participant (patient) is not aware whether he belongs to the study group or control group

And

Observer (doctor) also is not aware whether he belongs to the study group or control group

And

Interpretor (epidemiologist) too is not aware whether he belongs to the study group or control group

Eliminates Subject Bias, observer Bias and also Evaluation Bias

Tips

Other types of Bias include

  1. Recall Bias
  2. Sampling Bias
  3. Selection Bias

No comments:

Post a Comment