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Statistics Data (Central Tendency (Mean (average) (Weighted Mean (2 ways…

- - - - Multimodal- a distribution with more than 2 modes
      - Bimodal- a distribution with 2 modes
  - - - extreme scores/out liers
      - undetermined scores
      - data from ordinal scale
    - - discrete median is a whole number ie. x=4 (because indivisible)
      - precise median typically for continuous variable (X usually correspond to an interval)
        
        use fraction or interpolation to find precise median
  - - - weighted means can help with decisions where some things are more important than others
      - When some values get more weight than others,
        the central point (the mean) can change
      - 2 ways to compute weighted mean
        
        option 1: combine 2 sets of scores, then find the overall mean for the combined group
        
        option 2: use interpolation
  - - - have 1 mode, all 3 meaures of central tendency (mean, median, mode) are clustured together in the center of distribution
      - mean=median
    - - Negative skewed (tail to the left)
        Mean usually less than median
      - Positive skewed (tail to the right)
        Mean is usually greater than the median
- - - - the sum of the squared deviation or sum of squares (SS)
        
        degrees of freedom (df) = n-1
        
        df determine the number of scores in the sample that are independent and free to vary
    - - distance covered by the scores in a distribution from smallest score to the largest score
        
        when scores are measurement of continuous variable the range is the difference between the upper real limit for the largest score and the lower real limit for the smallest score (ie. 0.5 to 4.5 if range was from 1-4)
    - - most commonly used and most important measure of variability
        
        use the mean of distribution as a reference point
        
        provides a measure of the standard or average distance from the mean
        
        describes whether the scores are clustered closely around the mean or are widely scattered
  - - - clustered close together
      - spread out over a large range
    - - variability provides info about how much error to expect if using a sample to represent a population
  - - - if average value of the statistic is equal to the population parameter
    - - underestimates corresponding population parameter
      - overestimates corresponding population parameter
      - to rectify biased in sample variance, use degrees of freedom (n-1)