2 Flashcards
(25 cards)
what is a measure of location?
-a single value which describes a position in a data set
what is a measure of central tendency?
-when the single value describes the centre of the data
mode definition
-the value or class that occurs most often
median definition
-the middle value when the data values are put in order
when is it best to use the mode?
when data is qualitative or quantitative with either a single mode or 2 modes (bimodal)
when is it not helpful to use the mode?
-if each value in a data set occurs only once
when is it best to use the median value?
-for quantitative data
-when there are extreme values (as they dont affect it)
when is it best to use the mean value in a data set? [And why]
-for quantitative data
-uses all pieces of data to gives true measure of data
when is it not good to use the mean
-when the data set contains extreme values as these affect the mean
interpercentile range definition
-the difference between the values for 2 given percentiles
range definition
-difference between largest and smallest values in data set
interquartile range definition
-difference between the upper quartile and the lower quartile
IQR benefit
-not affected by extreme values
IQR cons
-only considers spread of middle 50% of data
range pros
-takes into account all of data
range con
-can be affected by extreme values
Rule for calculating Quartile values (for discrete data)
-add 1 to total frequency and then calculate
-if number is whole number then choose value between this data point and the one above (eg if 5 choose midpoint of 5th and 6th value)
-if num is not a whole number, round up and pick this data point (eg if 5.3 choose 6th value)
How to determine whether to use standard deviation or IQR
-determine which one has less variation by calculating difference
-use one with less variation
What does adding and subtracting numbers in coding do to the standard deviation?
-nothing
Does adding and subtracting numbers in coding affect the mean?
yes
Does mutiplying and dividing in coding affect the standard deviation?
-yes
Does mutiplying and dividing in coding affect the mean?
-yes
What happens to the variance is the data is mutiplied by 3?
-the variance is multiplied by 9
Measures of central tendency (3)
-mean
-median
-mode
