The t Tests

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The t Tests

• Review

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Which test?

• Specify the appropriate t test.
• College students are randomly assigned to undergo
  either behavioral therapy or Gestalt therapy.
  After 20 therapeutic sessions, each student earns
  a score on a mental health questionnaire.
• According to the U.S. Department of Health and
  Human Services, the average 16-year-old male can
  do 23 push-ups. A physical education instructor
  finds that in his school district, 30 randomly
  selected 16-year-old males can do an average of
  28 push-ups.
• One hundred college freshmen are randomly
  assigned to sophomore roommates having either
  similar or dissimilar vocational goals. At the
  end of their freshman year, the GPAs of these 100
  freshmen are to be analyzed on the basis of the
  previous distinction.
• A counseling program randomly selects 15 new
  mothers and measures their levels of depression,
  provides them with a counseling program, and
  measures their levels of depression again.

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Comparison of paired to independent sample t-test
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Paired samples t-test

• Perform paired samples t-test
• Calculate 95 CI

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Independent samples t-test

• Perform independent samples t-test
• Calculate 95 CI

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Question

• Why is the paired samples t-test significant?
• The difference is the same

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Group Practice
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Final Exam

• Study Guide will be posted this afternoon
• Homework answers will be posted Thursday
  afternoon
• Make sure that you can calculate following
• One sample t-test
• Paired samples t-test
• Independent samples t-test
• Make sure you can interpret the output for each.