QCLEC- Statistical control

• Definition of Terms

  • Statistics- concern collection, organization, interpretation and presentation of data
  • Mean- average
  • Standard deviation- spread data around mean
  • Same average = different standard deviation
• Statistical quality control

  • Control chart- influences decisions related to the function of specification production or inspection
  • Steps

  1. proper sampling
  2. quality variation
  3. interference to the entire batch under investigation= disposition
• Benefits of statistical quality control

  • detection of error
  • uniform quality
  • reduce inspection cost
  • reduce no. of rejects & save cost
  • basis of attainable specification
  • means of capability of manufacturing process
  • understanding and appreciation of quality control
• Methodology

  • Descriptive statistics- quality characteristics
  • acceptance sampling- batch sampling by investigation
  • SPC- inspecting random sample of output from process for characteristics
• Cause and effect diagram

  • Used to processes to achieve goal

  
• Scatter or XY diagram

  • relationship or correlation
  • causation= high index and high income
  • if data fall in the line = correlation
  • relationship- high index and indirect

  
• Pareto chart

  • descending from highest to lowest
  • problem solving addressed immediately

  
• Stratification

  • sorts data to find pattern

  
• Defect concentration/ check sheet

  • one person assigned

  
• Basic quality control charts

  • Variable data - actual measurement ( tablet wt.)
  • subgroup data - data gathered from units produced under conditions
  • X bar chart - process level, average of batch
  • R bar chart - range, detects unexpected variation
  • S chart - standard deviation
  • l chart- individual chart
  • m chart - moving range over time, lacks variation
  • attribute - not easy to be measured
  • sub group - certain no. of products that produced in same environment
• Control charts

  A) Variables

  B) Attribute

  C) Range

  D) items

  E) per unit

  F) p

  G) defective

  H) np

  I) constant

  J) U

  
• QUALITY CONTROL CHART

  A) Special variation

  B) common