Descriptive: Central Tendency and Measures of Dispersion Flashcards
What are measures of dispersion?
Range, variance, inter-quartile range
Where does the mean tend to lie and do outliers have an effect?
Its usually in the middle, however it is very sensitive to outliers and will always move towards them.
What is the median?
it is the central score once the values have been arranged in numerical order.
When there is an even number of scores, the median is found by finding the mean of the two central scores
Is the median affected by outliers?
It is much less affected than the mean is
What is the mode?
It is the value that occurs most frequently
What do central tendencies show?
they show averages
What are measures of dispersion?
tries to display the amount of variance across the scores
Why do some researchers prefer to use the inter-quartile range instead of just range?
Range is highly affected by extreme outliers and the inter-quartile range only considers the middle 50% of the range missing out any extreme outliers
How do you find the inter-quartile range?
You remove the lowest and highest 25% of the scores and then with the remaining middle 50%, you find the range
What are the estimates of central tendency?
Mean, Median, Mode
What is Variance?
It is a formula that shows us how much variation in the scores there is from the mean. It is an average of the variations.
How is the variance worked out?
- Calculate the mean
- Calculate how much each score deviates from the mean
- Square each deviation
- Then do a sum of all the squares
- Divide the sum by the number of scores
Important things to remember about Variance
Variance cannot be interpreted in isolation - it always applies to that particular set of data
no absolute scale
wide numerical scale will have a large variance and vice-versa
variance is often reported comparatively
