Statistics

Statistics

Descriptive Statistics
1. Measures of Central Tendency
  1. Three Kinds
    1. Mean
    2. Median
    3. Mode
2. Measures of Dispersion
  1. A measure of variability within the data
    1. Standard Deviation
    2. Variance
3. From means and SD
  1. Z-scores
    1. Compare a range of measurements
    2. Express how many SD units a point in the normal curve is from the mean
    3. A z-score is the number of SD units a score is from the mean
  2. Summarise data visually
4. Populations
  1. Every single possible observation
  2. We know how these tend to be distributed
5. Samples
  1. Make inference about the population from the sample
  2. Summarise from sample data what population mean is
  3. Central Limit Theorem
    1. Representative samples
      1. sampling distribution approaches normal distribution
      2. Mean of all sample means equals population mean
      3. Sample size increases, SD of sampling distribution decreases
    2. Sample size increase (n=30 min.) = more certainty of population mean
  4. Standard Error
    1. Confidence that sample mean represents population mean
Inferential Statistics
1. Basic Principles
  1. Test statistic
    1. How different your sample is from another mean
  2. Critical value
  3. Alpha level
    1. p<0.05
  4. Test statistic < critical value at alpha level = significant results
2. Errors
  1. Type I
    1. Too loose alpha level
      1. Less harmful for Data Analysis
  2. Type II
    1. Too strict alpha level
      1. Very harmful for Data Analysis
3. t-tests
  1. Uses
    1. Single sample is drawn from a population where mean is known
      1. Between samples t-test
    2. Two sets of measurements are drawn from same population
      1. In different groups
        Independent samples t-test
      2. Before and after intervention
        Paired samples t-test
    3. Quantifying the differences between actual and expected data

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	Created by natalieclark29 about 12 years ago

	Copied by Souradipta Chowdhury over 5 years ago