2.3 Measures of Central Tendency Flashcards
Measure of Central Tendency
A value that represents a typical, or Central entry of a data set.
Mean (know definition)
Sum of the entries divided by the total number of entries; best describes data sets with entries that are close together.
highest # - lowest # = mean
Sigma Notation
ΣX add all entries together
ΣX is capital sigma summation.
Population Mean
μ = ΣX/N
μ = Mu
Sample Mean
x̄ =ΣX/N
x̄ = x bar
Median (know definition)
- Middle entry of an ordered data set.
- Best describes data sets when there are many identical entries.
Outlier (know definition)
A data entry that is far removed from the other entries in the data set.
Advantage of using the mean
The mean is a reliable measure because it takes into account every entry of a data set.
Disadvantage of using the mean
Greatly affected by outliers (a data entry that is far removed from the entries in the data set)
Weighted Mean
The mean of a data set whose entries have varying weights.
x̄ = Σ (x•w)/Σw
Symmetric distribution
A vertical line can be drawn through the middle of the graph and the resulting halves are approximately mirror images.
Mean, median, and mode are equal.
Uniform Distribution (rectangular)
- All entries in the distribution have equal or approximately equal frequencies
- mean and median are equal
Skewed right distribution (positively skewed)
The “tail” of the graph elongated more to the right.
Sample standard deviation symbol
Sx
Sample variance symbol
Sx²
Population standard deviance
Ox
Population variance symbol
Ox²
Mean symbol
x̄
Mode (know definition)
Data entry that occurs the most.
Best describes data sets when there are many identical entries.
