Q-QUIZ MAY 2019

Mind the trap! Typical sources of error

There are numerous sources of errors when dealing with statistical procedures. Are you able to identify them and assess them correctly?

1. You analyse the relation between the process characteristic “holding pressure“ and the product characteristic “length“ of the produced part in an injection moulding process. The holding pressure of each part was recorded in the production process; all parts were stacked on a pallet afterwards. The parts are transported to a test room for linear measurement. Operators start with the parts on top of the pallet and record the values of all linear measurements in their testing sequence. Where is the error?

  • Missing target and task
  • Incorrect assignment of characteristic values
  • Falsification of original values

 

2. A product is still in development stage. You collected 30 values per characteristic. A Master Black Belt is entrusted with the calculation of “statistics“. What is the problem?

  • Missing target and task
  • Inadmissible conclusion about the population drawn from the subgroup
  • Insufficient resolution of the measurement system

 

3. The stitching of some clothes is evaluated in an incoming goods inspection. You take a sample of five items from a lot of 500 items. The lot is finally assessed to be free from defects since the sample did not include any defective units. What is the issue here?

  • Falsification of original values
  • Inadmissible conclusion about the population drawn from the subgroup
  • Insufficient resolution of the measurement system

 

4. All characteristics and specification limits are plotted in a graphic of individuals. Since the percentage of values exceeding specification limits was only 10%, you delete these values because you consider them to be outliers.

  • Incorrect assignment of characteristic values
  • Falsification of original values
  • Inadmissible conclusion about the population drawn from the subgroup

 

5. To measure the length of steel pins, you defined a tolerance of 0.05mm and introduced a x ̅-s control chart. You use a micrometre with a resolution of 0.01mm to take the measurements.

  • Missing target and task
  • Incorrect assignment of characteristic values
  • Insufficient resolution of the measurement system

 

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