What are the 2 measures?
Measures of central tendency
Measures of dispersion
Measures of central tendency?
Mean, median and mode
Measures of dispersion?
Range and standard deviation
Mean- strengths and weaknesses
S- makes use of all data available, gives us a true average, allows us further statistical analysis to be calculated
W- extreme scores in data can skew a mean score calculation which may result in a whole number of fraction that is in the actual data set.
Median- strengths and weaknesses
S- remains relatively unaffected by an outlying values, something that affects the means so more appropriate to use when extreme scores occur
W- affected more by the sample as it is concerned with one number doesn’t consider all of the data
Mode- strengths and weaknesses
S- easiest measure to calculate, gives most common score in a data set and unaffected by extreme scores
W- possible to have more than one mode, may not be any model value so instead use median or mean if no extreme scores.
Range- strengths and weaknesses
S- gives an indication of the consistency, reliability of the data
Relatively easy to calculate in comparison to standard deviation
W- can be affected by extreme values as value at highest and lowest end of set are used and these may not actually reflect the data set accurately
Fail to take into account the distribution of the numbers meaning that it doesn’t indicate whether most numbers are closely grouped around the mean or spread evenly
Standard deviation- step by step calculation
- calculate the mean by adding all your data points together and divide by the total number of data points
- find the deviation, subtract the mean from each individual data point
- square deviation, square each number from step 2 to make them all positive
- sum of the square deviations, by adding up all the square deviations
- calculate the variance, divide the sum from step four by the total number of data
- square root, find the square root of the variance from step 5 to get the standard deviation
