Fish Bone or Ishikawa Tool For Root Cause Analysis…For Quality control


Most commonly and widely used  among 7 QC tool is Fish bone or Ishikawa tool for root cause analysis.

We need to list down the possible causes of a problem graphically so that everyone can understand. The Fish Bone diagram is a graphic tool that helps in displaying the possible causes of a problem or quality characteristic.

Usually Fish Bone diagram is also called as Cause & Effect diagram, but to differ here as Fish Bone diagram only gives the list of probable causes that may or may not affecting the quality parameter. Hence, I take it as a misnomer. The reason being, we need to establish the Cause & Effect relationship downstream using scatter plot or Design of Experiments and only after that we can say cause & effect relationship is established.

The Fish Bone diagram helps in listing down the possible causes of variation through group discussion. It presents the list in a pictorial form, which is easily understandable, it also increases process understanding and tells us to collect the data for possible causes of variation.

It also categorizes the all possible causes of variation in 5 broad categories known as 5M

Men (problem because of Human Factor)

Material (problem because of raw material/ Others)

Machine (Problem due to Machine)

Methods (problem due to the measurement system or the process)

Measurements (problem related to Instrument Measurements)



1. MEN ( Human Factors)

–       Training

–       Analyst qualification in the particular test

–       Analyst Interview

o  Procedure followed

o  System verification

o  Data review

–       Solution preparation

o  Accuracy

o  Technique

o  Expiry

o  Storage condition

o  Segregation

–       Work load


–       Instrument Qualification

–       Instrument performance

o  Lamp Energy

o  Leaks

–      Electrical Spike

–      Instrument Calibration

o  Calibration validity (Done on and next due on)

o  List of OOC

o  Instrument failure history

o  Preventive maintenance ( Done on and next due on)

o  AMC

–       Instrument Setting & Parameters

o  Flow Rate

o  Detector

o  Temperature

o  Sample set

–       Autosampler

o  Vial positions

o  Vial Labeling

o  No of Injections per vial

3. Method

–       Method & sequence verification

–       Analytical Method validation

o  Solution stability

o  Robustness

–       Additional Experiments

–       Sample Conditions

o  Storage

o  Sample solubility

o  Sample dilution ( If any)

o  Sample preparation


–       Glassware

o  Contamination

o  HPLC / GC vials

o  Extraction tube

o  Validity of the filters used

o  Volumetric Glassware

–       Column

o  Usage Details ( No .of Injections)

o  Condition


–       Detector

o  Performance ( Noise, spike)

–      CDMS ( Cinematographic Data Management System)

o  Integration parameters

o  Calculation

o  Degradation

o  Late eluting peaks

o  Trend

–       System Suitability

o  % RSD

o  Tailing factor

o  Bracketing standard

o  Similarity Factor

–       Other Data Review

o  Other Test ( Assay/ DCU/Elution)

o  Additional batches

o  Historical data


–       Room Temperature

–       Humidity


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