Levels of measurement Flashcards
Nominal
Numerals represent category labels only
Do not imply an order
E.g gender
Ordinal
Numbers indicate rank order of observations
e.g 1st place
E.g questionnaires
Interval
Order and equal intervals between numbers but not related to true zero
e.g IQ
Ratio
Numbers represent units with equal intervals, measured from true zero
Can have value of 0 unlike the others
0 indicated absence of the quantity being measured
E.g age
Mean
Score that occurs the most frequently
Mode
The score that occurs the most frequently in a distribution
Median
the middle score when the scores have been ranked
Interquartile range
Quartiles divide a distribution into 4 equal parts
Distance between Q1 and Q3 is the IQR
How do you calculate the inter quartile range
find mean
subtract mean from each score
square each difference score found in step 2
add all the squares
divide the total by (numbers of scores - 1 )
Uses part of each score in calculating the spread and is used in parametric statistical scores
Coefficient of variation
Used to describe data measured on the interval or ration scale, expressed as a percentage
=standard deviation / mean x 100
normalised measure of spread independent of the measurement used
When is it better to use coefficient of variation than SD
When you want to compare the spread in 2 or more sets of scores which use different units
Descriptive statistics
Measures of central tendency
Measures of data spread
Distribution of the data
Used to describe and summarise the characteristics of the same, heck variables for violation of assumptions underlying statistical techniques
Kurtosis
The peakedness of the distribution
Positive kurtosis = distribution peaked with long thin tails
Negative kurtosis = distribution flat with lots of extreme cases
Skewness and kurtosis can sometimes be removed by transforming the data or it can be measured
