Measures of central tendency and dispersion Flashcards
1
Q
What is central tendency ?
A
Measure averages which tell us about the most typical values.
2
Q
What are the three main types of central tendency ?
A
- Mean
- Median
- Mode
3
Q
Mean
A
- often known as the average
- Calculated by: adding up all the values and dividing it by the amount of scores
- strength - most representative as it includes all the values
- Limitation - easily distorted by extreme values
4
Q
Media
A
- The middle number in a data set when the socres are arranged from lowest to highest
- stregth - extreme scores have no effect
- strength - easily calculated
- limitation - actual values of lower and higher figures are ignored
- limitation - the extreme values may be important
5
Q
Mode
A
- The most frequently occurring value in a data set
- There can be two-modes (bi-modal) or no modes
- strength - easy to calculate
- limitation - not representative
- limitation - if bi-modal - the two modes can be very different
6
Q
What are the measure sof dispersion ?
A
Any measure of the spread or variation in a set of scores
7
Q
What are the two types of measures of dispersion ?
A
- range
- standard deviation
8
Q
Range
A
- A calculation of the spread of the scores
- Taking the highest number away from the lowest +1
- Adding 1 is a mathematical correction as raw scores are often rounded up
- Strength - easy to calculate
- Limitation - only looks at the two most extreme values (unrepresentative)
- Limitation - doesn’t indicate whether numbers are closely groups or very spread out values
9
Q
Standard deviation
A
- ‘More sophisticated’ measure of dispersion
- tells us how much as single value deviates from the mean
- larger standard deviation = more dispersion, this suggests not all participants are affected by the independent variable may be a few anomalous results)
- low standard deviation means that the participants were affected similarly
- Strength - more precise than the range
- Limitation - can be distorted by an extreme value
