Lets Have a Cup of Tea

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Lets Have a Cup of Tea!

• Minjuan Wang
• ED 690

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T test Video

• 21. Inference for One Mean
• the t statistic for use when s is not known.
  Emphasis is on paired samples and the t
  confidence test and interval..
• 22. Comparing Two Means
• How to recognize a two-sample problem and how to
  distinguish such problems from one- and
  paired-sample situations are the subject of this
  program.

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Paired Samples T Test (T for one)

• Inference for One Mean
• http//learner.org/resources/series65.html?popyes
  vodid328482pid159
• Watch minutes 1230 to 2058
• Paired t test on neutralsweet
• Taste evaluation
• One right after it is made
• One after 4 months
• H0 no differences in sweetness
• Ha one-tailed test (there are differences)
• Before and after- sweetness values from each
  panelists
• Calculate p (probability of chance)

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Independent Samples (Tea for Two)

• Comparing Two Means
• http//learner.org/resources/series65.html?popyes
  vodid328482pid159
• Do women make more money after participating in
  the Options program in Baltimore? (a 3-year
  study)
• Watch the beginning 10-11 minutes
• N1398
• The dataset will be too large for us to practice
  in class.
• Pay attention to the t calculation on video

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• T(ea) for One (flow chart p. 208 of Salkind)
• T test for dependent samples (paired t test)
• To test hypothesis
• Examine changes between one group of participant
  (or two matched pairs) on one or more variables
• To compare if there is significant change in the
  means of the variables studied
• Example
• (Not significant) attitude change of 21 youth
  before and after their participation in
  Expeditions
• Significant change in self-confidence and
  competence
• 10 patients going through a 2-hour psychotherapy
• 
  

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Types of T(ea) for One

• Repeated measures
• Matched pairs
• Two groups matched on critical variables
• Example
• E-classroom on fire
• Compare the occurring frequency of flaming and
  buffoonery in traditional and E classrooms
• Content analysis of discussions (counting)
• Which test to use?

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Interpretation (Results)

• Level of significance
• Indicates how much the differences found are due
  to chance rather than intervention
• Usually set at 5 (a 0.05)
• Shown as Confidence interval 95
• Attitudinal gains (change)?
• P gt 0.05
• Learning Gains?
• P lt0.05

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T(ea) for Two

• Flow chart p. 194 of Salkind)
• T test for independent samples (unpaired t)
• Test for a difference
• Examine differences between two groups of
  participants on one or more variables
• To compare if there is significant difference
  between the means of the variables studied
• Examples
• Mid-term scores of class A and class B
• User engagement in two types of multimedia
  training systems
• The article on user engagement
  
• 
  

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Type of T(ea) for Two

• Archetypal experiment
• Randomly selected and assigned to 2 groups
• Anti-depression drug versus placebo
• T to compare mean differences on a depression
  measurement scale
• In Situ design
• Pre-assigned to 2 groups by nature or God
• Insomnia on work efficiency
• Gender and

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• T(ea) for Two

• Is there significant difference in the intensity
  of eating disorder across different cultures
• 297 Australian-gt249 Indian University students
• Eating Attitudes Test and Goldfarb Fear of Fat
  Scale
• To measure Intensity of eating disorder
• Run t test for independent samples (unpaired
  t-test)
• Any difference on the mean of eating attitude
  scores
• Any difference on the mean of Fear of Fat scores

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Interpretation

• Results
• Descriptive
• Indian students scored higher on both of the
  tests (higher intensity)
• Is the mean difference statistically significant?
  
• Take it to unpaired t test for independent
  samples
• T (eating attitude) -4.19, p lt .0001
• T (fear of fat) -7.64, P lt 0.0001

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Conclusion

• Judge by P value
• The probability that the difference is due to
  chance
• P lt 0.0001 (very small chance that the
  differences are due to things other than group
  membership)
• There are significant differences between
  Australian and Indian students in their intensity
  of eating disorder.