Statistics applied to Quality Control

Statistics applied to Quality Control

1. Cause and Effect Diagrams

   • Know as Fishbone Diagrams
   • This method forces the user to consider all the likely causes of a problem
   • It works with backwards along the spines
   • combine brainstorming techniques with graphical analysis

2. Control Chats

   • known as Shewhart charts or process-behaviour charts
   • is a specific kind of run chart that allow
   • Is objective and disciplined approach that enables correct decisions regarding control of the process

3. Stratified sampling

   • From a population
   • It is not useful when there are no similar subgroups
   • Stratification
     • is the process of dividing members of the population into homogeneous subgroups before sampling.

4. Check Sheet

   • simple document
   • Tis can be quick, easy, and efficient recording of the desired information
   • Can be called tally sheet
   • The types depends on their classification, location, frecuency Measurement Scale and Check List

5. Scatter Plots

   • This use Cartesian coordinates to display values for two variables for a set of data.
   • We can use when a variable exists that is under the control of the experimenter
   • Correlations may be positive (rising), negative (falling), or null (uncorrelated)

6. Histogram

   • Is a graphical representation, showing a visual impression of the distribution of data.
   • Consists of tabular frequencies, shown as adjacent rectangles, erected over discrete intervals (bins), with an area equal to the frequency of the observations in the interval
   • Are used to plot density of data
     • estimating the probability density function of the underlying variable

7. Pareto chart

   • is a type of chart that contains both bars and a line graph
   • Highlight the most important among a (typically large) set of factors.
   • The left vertical axis is the frequency of occurrence, but it can alternatively represent cost or another important unit of measure.
   • The right vertical axis is the cumulative percentage of the total number of occurrences, total cost, or total of the particular unit of measure

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