Measures of central tendency

another type of descriptive statistic for presenting interval and ratio scales or data from the sample under study.
1. Variables that use interval/ratio scales
  1. distribution of the data might be of less interest to the researcher than an overall summary of the scores.
form an index or summary numbers that describe the middle of a distribution of sample data.
Mean
1. Equal to the sum of all values divided by the number of participants.
  1. Sensitive to extreme values, also known as outliers
    1. Not appropriate for data that differs greatly from normal (bell shaped) distribution, as in a skewed distribution.
      1. If the mean differs meaningfully from the median it suggests that the distribution is skewed (not normal).
Mode
1. value that occurs most frequently.
2. used for categorical variables or data,
3. particularly when categories are not naturally ranked (nominal).
Median
1. middle value in a ranked list
2. point in the distribution above which and below which 50% of the cases fall.
3. not sensitive to extreme values or outliers. When
4. distribution is highly skewed the median provides a better measure of central tendency
5. Middle value
Measures of disperson
1. Are a type of descriptive statistic
2. Describe the spread of observations/data about the mean
3. Are ways of presenting the data spread or dispersion of data in a sample
4. Are used because for some sample data measures of central tendency do not give a total picture of the data spread

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