Statistics - Representations of data Flashcards
What is an outlier?
An extreme value that lies outside overall pattern of data
What are the common definition of an outlier?
Any value that is:
Greater Q3 + k x IQR
Less than Q1 - k x IQR
What is an anomaly?
Outlier that is removed from data since it is clearly an error and it would be misleading to keep it
What is cleaning the data?
The process of removing anomalies from a data set
What features does a box plot show with lines?
Lowest value
Highest value
Q1, Q2, Q3
Outliers are a cross
What should be done when comparing two box plots?
Use the same scale
Compare medians, IQR and extremes
What is bivariate data?
Data which has pairs of values for two variables
What is usually plotted on each axis?
x-axis - independent variable
y-axis - dependent variable
What is a causal relationship?
When a change in one variable causes a change in the other
Correlation doesn’t show causation
What is the regression line?
Straight line that minimises the sum of the squares of the distance of each data point from the line
What is the equation of the regression line?
y = a + bx
When should you use a regression line to make predictions?
When values are within the range of the given data
What are histograms used for?
Continuous variables
What is the equation for frequency density?
Frequency density = frequency / class width
What is the equation for frequency and area?
Frequency = k x area of the bar
What does unimodal mean?
Data has one point where the distribution peaks
What does bimodal mean?
Two points in data where the distribution peaks
What is bivariate data?
Data made up of pairs
x,y
What is a scatter diagram?
Each variable is plotted along one of the axes
What are scatter diagrams used for?
Showing whether data is correlated
What is important to remember about correlation?
Correlation does not mean causation
Could be linked by another factor
What is linear regression?
Process used to find equation of regression line (line of best fit)
What is the explanatory variable?
Independent variable - variable which is affecting the other, always on horizontal axis
What is the response variable?
Dependent variable - variable being affected, always on vertical axis
