DATA INTERPRETATION

This page will describe several simple tools which will be useful for you in inperpreting data. If you have access to the www (world wide web), the links (always underlined) will give you further information.

PIE CHARTS

• DISPLAYS DATA IN THE FORM OF A CIRCLE
• PERCENT OF TIME EVENT OCCURS INDICATED BY A WEDGE OF THE PIE
• NOTE SCALES WHEN COMPARING MORE THAN ONE CHART
• CAN BE 3 DIMENSIONAL
• USEFUL FOR VISUALIZING PERCENTAGE DATA

BAR CHART

• A CHART WHERE EACH BAR REPRESENTS FREQUENCY OF OCCURANCE
• RELATIVE POSITION OF BARS UNIMPORTANT TO CHART INTERPRETATION (SEE HISTOGRAM FOR DIFFERENCE)

LONGER BARS REPRESENT GREATER FREQUENCIES

HISTOGRAMS

• A SPECIAL KIND OF BAR DIAGRAM
• GRAPHICALLY REPRESENTS THE VARIATION IN A GIVEN SET OF DATA
• SHOWS THE FREQUENCY OF OBSERVATIONS WITHIN A SUBGROUP
• SUBGROUPS IN EITHER ASCENDING OR DECENDING ORDER ON THE X AXIS

PARETO CHART

• A SPECIAL KIND OF HISTOGRAM
• THE PRINCIPLE OF THE VITAL FEW
• PLOTS DATA FROM HIGHEST FREQUENCY TO THE LOWEST
• COSTLY PROBLEMS STAND OUT
• EASY TO UNDERSTAND

TIME SERIES (CYCLE HISTORY)

• GRAPHICAL PLOTTING OF DATA OVER TIME
• SOMETIMES CALLED A RUN CHART
• ALLOWS YOU TO SEE THE PATTERN OF OUTPUT OVER TIME
• HOW TO CONSTRUCT
• IDENTIFY MEASUREMENT TO BE MONITORED
• TAKE SAMPLES OF THE OUTPUT
• COLLECT THE DATA
• EXAMINE THE RANGE OF THE DATA; RANGE = HIGH - LOW VALUES
• PLOT THE POINTS ON THE CHART AND CONNECT THEM
• COMPUTE THE AVERAGE OF ALL PLOTTED POINTS AND DRAW IT AS A HORIZONTAL LINE THROUGH THE DATA
• INTERPRET: IF THE PLOTTED POINTS FLUCTUATE IN A STABLE PATTERN AROUND THE CENTER LINE, WITH NO LARGE SPIKES, TRENDS, OR SHIFTS, THE PROCESS IS LIKELY TO BE UNDER CONTROL

CONTROL CHART

• A RUN CHART WITH CONTROL LIMITS
• CONTROL LIMITS ARE ACTION LIMITS, OR POINTS TO TELL YOU WHEN TO TAKE ACTION
• SET USING RULES OF CHANCE (SOMETIMES CALLED STATISTICS)

TABLES

• SPREADSHEETS WHICH RELATIONSHIPS BETWEEN TWO VARIABLES
• TYPICALLY ACROSS THE COLUMNS ARE THE DIFFERENT CATEGORIES AND ACROSS THE ROWS ARE INDIVIDUAL RECORDS WITHIN THOSE CATEGORIES
• GOOD SUMMARY TOOL
• ROWS AND COLUMNS MAY BE INDEPENDANT
• MAY MANIPULATE ROWS AND COLUMNS TO OBTAIN A BETTER PICTURE OF THE DATA
• KEY ELEMENT IN DATA BASES

SCATTER DIAGRAMS

• SHOW RELATIONSHIPS BETWEEN VARIABLES
• DIFFERENT LEVELS OF TWO DIFFERENT VARIABLES SHOWN ON HORIZONTAL AND VERTICAL AXES
• DOES THE OUTPUT OF ONE INFLUENCE THE OUTPUT OF THE OTHER?

FLOW CHARTS

• SHOWS THE STEPS INVOLVED IN A PROCESS
• HELP YOU TO UNDERSTAND A PROCESS OR TO STANDARDIZE THE PROCESS
• HELP TO IMPROVE HOW YOU DO THINGS: ASK WHY?, WHERE?, WHEN? , HOW?

CHECKLISTS

• SPECIAL TYPES OF DATA COLLECTION FORMS IN WHICH THE RESULTS MAY BE INTEPRETED WITHOUT ADDITIONAL DATA PROCESSING
• EXAMPLES
• STEM AND LEAF CHART
• TALLY IN SPECIFIC CATEGORIES
• DEFECT LOCATION SHEET

BRAINSTORMING

• GROUP PROCESS FOR GENERATING IDEAS
• NO EVALUATION PERMITTED
• NO BOUNDS PLACED ON IDEA GENERATION

CAUSE AND EFFECT DIAGRAMS

• AIMED AT DETERMINING THE ROOT CAUSE OF PROBLEMS
• A TREE DIAGRAM WHERE THE PROBLEM IS INDICATING AND POTENTIAL CAUSES ARE NOTED, AND SUBCAUSES ARE NOTED

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This page created by David Lewis on 7/3/97