Measures Of Central Tendency & Dispersion Flashcards
What are descriptive statistics?
use of summary statistics to identify trends & analyse sets of data
What are measures of central tendency?
- the general term for any measure of the average value in a set of date
- mode, median, mean
What is the mean and how is it calculated?
arithmetic average calculated by adding up all values then dividing by total number of values
What is a strength and limitation of using the mean?
strengths
- most sensitive of the measures as it includes all the values in data set within the calculation
limitation
- mean is easily distorted by extreme values which may not represent the data set overall
What is the median and how is it calculated?
the middle value in a data set when scores are arranged from lowest to highest
What are the strengths and limitations of using the median?
strengths
- not affected by extreme scores
- easy to calculate
limitation
- less sensitive (actual values of lower & higher numbers are ignored)
What is the mode?
the most frequent value in a data set
What are the strengths and limitations of using the mode?
strengths
- sometimes the only method of measure u can use (data in categories)
- easy to calculate
limitations
- not useful if there are many different modes
- not representative of the whole data set
What is meant by measure of dispersion?
- the general term for any measure of the spread or variation in a set of scores
- range, standard deviation
What is the range and how is it calculated?
calculation of the spread of scores and is worked out by subtracting the lowest value from the highest value and adding 1 (accounts for margin error)
What are the strengths and limitations of using the range?
strength
- easy to calculate
limitations
- only takes into account the most extreme values >unrepresentative of the data set as a whole
- range is influenced by outliers (distorted by extreme values)
- does not indicate whether most numbers are closely grouped around the mean or spread out
What is standard deviation?
- more sophisticated measure of the spread of set of scores
- tells us how far scores deviate from the mean
What are the strengths and limitations of using standard deviation?
strengths
- much more precise measure of dispersion as it includes all the values within final calculation
limitation
- can be distorted by a single extreme value > not representative
What does a low standard deviation suggests?
- reflects the fact that the data is tightly clustered around the mean
- may imply that all participants responded in a fairly similar way
What does a high standard deviation suggest?
- the spread of scores is much greater
- not all participants were affected by the IV in the same way
- may be a few anomalous results
