Paired t-test Exercise

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Paired t-test Exercise

• Exercise objective Utilize what you have learned
  to conduct and analyze a paired t-test using
  MINITABTM.
• 1. A corrugated packaging company produces
  material which has creases to make boxes easier
  to fold. It is a critical to quality
  characteristic to have a predictable Relative
  Crease Strength. The quality manager is having
  her lab test some samples labeled 1-11. Then
  those same samples are being sent to her
  colleague at another facility who will report
  their measurements on those same 1-11 samples.
• 2. The US quality manager wants to know with 95
  confidence what the average difference is between
  the lab located in Texas and the lab located in
  Mexico when measuring Relative Crease Strength.
• 3. Use the data in columns Texas Mexico to
  determine the answer to the quality managers
  question.

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Paired t-test Exercise Solution

• Because the two labs ensured to exactly report
  measurement results for the same parts and the
  results were put in the correct corresponding
  row, we are able to do a paired t-test.
• The first thing we must do is create a new column
  with the difference between the two test results.
  

CalcgtCalculator
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Paired t-test Exercise Solution

• We must confirm the differences (now in a new
  calculated column) are from a Normal
  Distribution. This was confirmed with the
  Anderson-Darling Normality Test by doing a
  graphical summary under Basic Statistics.

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Paired t-test Exercise Solution

• As weve seen before, this 1 Sample T analysis is
  found with
• StatgtBasic Statgt1-sample T

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Paired t-test Exercise Solution

• Even though the Mean difference is 0.23, we have
  a 95 confidence interval that includes zero so
  we know the 1-sample t-tests null hypothesis was
  failed to be rejected. We cannot conclude the
  two labs have a difference in lab results.

The P-value is greater than 0.05 so we do not
have the 95 confidence we wanted to confirm a
difference in the lab Means. This confidence
interval could be reduced with more samples taken
next time and analyzed by both labs.