Quality Tools in Six Sigma

pareto principle

Limited number of causes often lead to majority of problems; 80/20 rule

Pareto chart steps

1. Tally number of defects for each category 2. Sort from highest to lowest frequency 3. Calculate the percentage each category contributes to total number of defects 4. Calculate cumulative percentage by adding each category’s percentage to the sum of the previous ones 5. Plot data on chart: left Y axis=number of defects; x axis=types of defects; right Y axis=cumulative percentages

cause and effect diagrams

fish bone diagram to gain a clear overview of potential causes to spot patterns and connections

man

people involved

machine

equipment and tools

method

procedures and work flows

material

raw materials and components

measurement

data collection and accuracy

mother nature

environmental factors

flow charts

highlight delays and breakdowns, reveal inefficiencies, & turn complex workflows into clear diagrams

Oval/circles

start or end of a process

Rectangles

task that moves process forward

Diamonds

decision points that usually asks a question

Parallelagrams

input or output

Flow chart steps

1. Define process starts and ends 2. Collect info on steps, decisions, and handoffs 3. Collaborate to gather team insights 4. Sequence steps with flowchart symbols 5. Review for accuracy

run charts

Understand how a process behaves overtime, Monitor process without complex tools, Use to validate improvements

run chart Y axis

measured values

run chart x axis

time intervals

Shift

seven or more consecutive points fall above or below median

Trend

steady increase or decrease over five or more points

Oscillation

rapid alternation around the median

Mixture

data points avoid the median

Clustering

data grouped in time

check sheets

organize data such as defects and locations using columns or sections to represent data categories and use tallies during data collection

designing check sheets steps

1. Define specific data categories related to the process 2. Guide collectors with clear, accurate category labels 3. Design simple user friendly check sheet layout 4. Include date and time to track 5. Enhance clarity with symbols and color coding

scatter diagrams

explores correlations between variables not visible in raw data

creating scatter diagram steps

• Select correct variables

• Define independent and dependent variables with clear examples

• Collect accurate data for both defined variables

• Use paired measurements under consistent data conditions

• Y axis = independent variable

• X axis = dependent variable