Statistics

Statistics

• Summarizes data → descriptive → cannot use to generalize

• Analyze + draw conclusions → inferential → generalize to large population (random sample)

• Common language

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Measure of central tendency: mean, median, mode

• Outlier when one or more data points are very different from the others
  • Leads to a skewed distribution
  • Median will be the best measure of central tendency to use
  • median > mean → negative skew
  • mean > median → positive skew

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Measures of variation

• Range = (largest number)-(lowest number)
• Standard deviation: measure of how dispersed the data is in relation to the mean
  • How spread out the data points are

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Normal distribution/curve (bell curve)

• Symmetric (no skew)
• Most data in the middle, less towards extremes
• Median = mode = mean
• 68% → 1 SD
• 95% → 2 SD
• 99% → 3 SD

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Inferential statistics: When can results be generalized?

• Sample is representative of population being studied (random sampling)
• More cases exist with those results (large sample size)
• Variability of the data is low

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Are the results due to differences in the IV or due to chance?

Statistical significance

• Calculated using a variety of statistical tools (Chi-square, T-test)
• How likely results are due to chance or differences in the IV
• NOT how important the results are
• Reported as a p-value
  • p-values of 0.05 or less → statistically significant, indicate results are not likely due to chance → can generalize to larger population
  • The results are unlikely to be obtained if there is no difference between the control and experimental groups

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