Descriptive Statistics Flashcards
What are descriptive statistics
The use of graphs, tables and summary statistics to identify trends and analyse sets of data
What are measures of central tendency and three examples
Averages which give information about the most typical values in a set of data eg mean,median and mode
How is the mean calculated
By adding up all the values in a data set and dividing this by the total number of values there are
Advantages of the mean
Most sensitive value as includes all values in the data set within the calculation, means it is representative of the data as a whole
Limitations of the mean
Easily distorted by extreme values
What is the median
Middle value in a data set when scores are arranged from lowest to highest
Advantages of the median
-extreme values do not distort it
-easy to calculate
Limitations of the median
Less sensitive than mean as not all scores are included in the final calculation
What is the mode
The most frequently occurring value within a data set, can be two modes(bi-modal) or no mode
Advantages of the mode
-very easy to calculate
-for data in categories it is the only method you can use
Limitations of the mode
-may not be representative of data as a whole as does not take into account all values
What are measures of dispersion and two examples
Based on the spread of scores which is how far scores vary and differ from one another eg range and standard variation
What is the range
Worked out by taking the lowest value from the highest and usually adding 1 which accounts for margins of error
Advantage of the range
Easy to calculate
Limitations of range
Only takes into account the two most extreme value meaning the range may be unrepresentative of the data set as a whole
What is standard deviation
Single value that tells us how far scores deviate from the mean, larger the SD=greater the dispersion
What do large and low standard deviations mean for an experiment
-large standard deviation suggests not all participants were affected by the IV in the same way, may be anomalous results
-low standard deviation reflects fact that the data is tightly clustered around the mean, all pps responded in a similar way
How to calculate standard deviation
Calculate the difference between the mean and each score and add up all the differences and divide this by the number of scores, standard deviation is the square root of the variance
Advantages of standard deviation
More precise measure of dispersion than range as includes all values within the final calculation
Limitations of standard deviation
Can be distorted by a single extreme value as it includes all values
