Week 3 Descriptive stats Flashcards
What is a nominal scale?
Subjects are grouped into mutually exclusive categories
Provide an example of a nominal scale
Gender Hair colour
What is an ordinal scale?
Ranks subjects/scores in order but doesn’t indicate how much better one score is to another
Provide an example of an ordinal scale
Position in a race
What is an interval scale?
Equal or intervals between data points on a sale, but there is no absolute zero point
Provide an example of an interval scale
Temperature
What is a ratio scale?
Equal units of measurement and an established zero point
Provide an example of a ratio scale
Height Weight
What are the measures of central tendency?
Mean Mode Median
What is standard deviation?
The average distance away from the mean
What does a low standard deviation value mean?
The better the mean describes the data
What is skewness?
A measure of lateral deviation form normality
Are skewed distributions symetrical?
No
What does it mean is the graph is positively skewed?
‘Tail’ of the distribution if positioned at the upper end of the score continuum
What does it mean if the graph is negatively skewed?
‘Tail’ of the distribution if positioned at the lower end of the score continuum
What is kurtosis?
A measure of vertical deviation from normality
What does it mean if a graph is leptokuritc?
Curve is more peaked than a normally distribited curve
What does it mean if a graph is platykurtic?
Curve is more flat than a normally distribited curve
What is the acceptable range of skewness?
-1 and +1
What is the acceptable range of kurtosis?
-1 and +2
What do z-score allow?
Compare variable with different units
How do z-scores work?
By calculating the number of SD’s away from the population mean.
How is the graph distributed?
Positively skewed
How is the graph distributed?
Negatively skewed
