Statistics applied to Quality Control

Statistics applied to Quality Control

1. Cause and Effect Diagrams

   • Also Known as
     • Ishikawa and Fishbone Diagrams
       • First used in the 1940´s
   • are employed to identify the underlying symptoms of a problem or effect
     • places the effect at one end
       • The causes feeding into it are then identified, via brainstormin

2. check sheet

   • is used for collecting data in real-time and at the location where the data is generated
     • the check sheet is sometimes called a tally sheet.
       • that data is recorded by making marks ("checks") on it.
   • 5 Basic types of Check Sheets
     • Classification
     • Location
     • Frequency
     • Measurement Scale
     • Check List:

3. Pareto chart

   • graph to organize data so that they are in descending order, from left to right and separated by bars
   • is a type of chart that contains both bars and a line graph
     • The purpose of the Pareto chart is to highlight the most important among a set of factors
       • They are often used to identify areas to focus on first for process improvement.

4. scatter plot

   • Is a type of mathematical diagram
     • It is used to study the association of two interval variables
   • A scatter plot is used when a variable exists that is under the control of the experimenter
     • ability to show nonlinear relationships between variables.

5. histogram

   • was first introduced by Karl Pearson
     • Is a graphical representation, showing a visual impression of the distribution of data
   • A histogram consists of
     • tabular frequencies
     • shown as adjacent rectangles
     • erected over discrete intervals

6. Stratified sampling

   • Is a method of sampling from a population
     • Advantages
       • it ensures each subgroup within the population receives proper representation within the sample.
       • Accurately Reflects Population Studied
   • Randomized stratification can also be used to improve population representativeness in a study.
     • Disadvantages
       • It is not useful when there are no similar subgroups
       • . It cannot be used when amount of data in subgroups is not equal

7. CHAVARRIA CASTRO DIANA KAREN

8. Control charts

   • used to determine whether or not a manufacturing or business process is in a state of statistical control
     • be differentiated from the natural variability of the process.
   • also known as
     • Shewhart charts or process-behaviour charts
       • enables correct decisions regarding control of the process

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