Measure of Variability.pptx
- 1. Measure of Variability Research 9 Special Science Class
- 2. Measure of Variability •It is used to determine the spread of scores in a distribution. It gives an idea of how much the scores deviate from the center of the distribution. •There are several measures of variability: range, mean deviation, variance, and standard deviation.
- 3. Measures of Variability There are several measures of variability: Range Mean Deviation Variance Standard Deviation
- 4. Range •It is the full distance between the lowest and highest scores in a distribution. •It is the easiest and the quickest to compute.
- 5. Range •It can be classified into: a. Exclusive Range – the difference between the highest score (HS) and the lowest score (LS) in the distribution, (HS – LS). b. Inclusive range – the difference between the highest score and lowest score plus one, (HS - LS + 1)
- 6. Mean Deviation •The mean deviation gives a rough estimate of the distances of the individual scores from the mean of the scores. It is the average of the absolute deviations of the scores from the mean.
- 7. Mean Deviation •The mean deviation gives a rough estimate of the distances of the individual scores from the mean of the scores. It is the average of the absolute deviations of the scores from the mean.
- 8. Mean Deviation •In mathematical form it is:
- 9. Mean Deviation •Steps in Getting the Mean Deviation: 1. Get the mean score. 2. Subtract the mean from each value. 3. Take the absolute value of each result. 4. Add them up. 5. Divide this value by the total number of observations or score.
- 10. Variance •Squaring deviations of scores from the mean gives positive squared deviations. You call this variability the variance of the set of scores. •You can numerically describe the consistency (precision) of measurement using variance. •This measures how far or close the measurements are from the mean (average.)
- 11. Variance •It is defined as the average of the squared difference of the measurement (𝑥) from the mean (𝑋). The formula to find variance is: 𝝈𝟐 = (𝑥−𝑋)2 𝑁
- 12. Variance •Below are the steps in finding the variance of a set of scores: 1. Find the mean of the scores. 2. Get the deviation of each score from the mean. 3. Square each deviation from the mean. 4. Get the sum of the squared deviations from the mean.
- 13. Variance •Continuation… 5. Divide this sum by the total number of scores. The quotient is the variance of the set of scores.Get the deviation of each score from the mean.
- 14. Variance •𝝈𝟐 = (𝑥−𝑋)2 𝑁 • Where N is the number of measurements done.