B AD 6243: Applied Univariate Statistics

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# B AD 6243: Applied Univariate Statistics - PowerPoint PPT Presentation

B AD 6243: Applied Univariate Statistics. Hypothesis Testing and the T-test Professor Laku Chidambaram Price College of Business University of Oklahoma. Steps in Hypothesis Testing. Determine hypotheses (null &amp; alternative) Select significance level (  level/p level) Choose a sample size

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### B AD 6243: Applied Univariate Statistics

Hypothesis Testing and the T-test

Professor Laku Chidambaram

University of Oklahoma

Steps in Hypothesis Testing
• Determine hypotheses (null & alternative)
• Select significance level ( level/p level)
• Choose a sample size
• Calculate the value of the statistic
• Obtain critical value
• Compare results

Errors in Hypothesis Testing

Sample (“Trial”)

Population (“Truth”)

MAXMINCON Principle
• Maximize experimental variance
• Design, plan and conduct research so that the experimental conditions are as different as possible
• Minimize error variance
• Reduce error through controlling experimental conditions
• Reduce error by increasing reliability of measures
• Control extraneous variance
• Randomization: Groups can be considered statistically equal in all possible ways
• Selection: To eliminate the effect of an extraneous variable on a dependent variable, choose subjects so that they are as homogenous as possible (on that variable)
• Addition: To control the effect of an extraneous variable, build it into the research design, so as to measure its effect on the dependent variable

Differences between Groups
• Randomized groups
• Random sampling; random assignment
• Simple vs. factorial designs
• Concerns:
• (Pre-experimental) equality of groups
• Unequal cell sizes
• Correlated group(s)
• Use same units in different treatments
• Single vs. multi-group designs
• Concerns:
• History, maturation and sensitization

Concepts Related to the T-test
• Degrees of freedom
• T-distribution vs. standard normal distribution
• Level of significance
• Between subjects design:
• Equal sample sizes
• Equal variance
• Within subjects design

Standard Normal Distribution

t Distributions

t-distributions refer to a family of distributions, which like normal distributions, are

bell-shaped, but whose shape changes with the sample size; smaller sample

sizes have flatter distributions, while larger sizes approximate normal distributions

Independent Samples t-test

Independent Samples Error Bar