RESEARCH METHODS - Descriptive statistics: measures of variability Flashcards
Define: measure of variability
A statistic that indicates how widely scores are spread around a central point (indicates variability)
Define: variability
how widely scores are spread around a central point
Define: low variability
When scores are tightly clustered around the mean, with very little spread of scores either side of the mean
Define: high variability
When scores are widely spread from the mean
Provide an example of low and high variability
Low: length of newborn infants
High: height of year 8 students
In what 3 ways can variability be measured?
range, variance and standard deviation
Define: range
the difference between the highest and lowest score in a set of scores (highest-lowest)
When is range useful and when is range not useful?
Useful for low variability; gives wrong impression if there are extreme scores
Define: variance (and how is it measured)
A descriptive statistic that represents in a general way the spread of scores around the mean (difference of score from mean)squared
When is variance useful and when is variance not useful?
Useful to provide general impression of scores, often for comparison; but is difficult to interpret
Define: standard deviation (and how is it measured)
A descriptive statistc that indicates how much, on average, a score differs from the mean
√(variance)
The higher the standard variation, the higher the __________
variability
When is standard deviation useful?
To provide a comparison between two scores, esp. if only a mean etc. is provided
