3.2d Presentation of data Flashcards
What do discrete and continuous variables give rise to?
qualitative, quantitive or ranked data
What is qualitative data?
subjective and descriptive
What is quantitive data?
can be measured objectively. usually with a numerical value
What is ranked data?
the data transformation in which numerical values are replaced by their rank when the data are sorted from lowest to highest
What impact does they type if variable have on presentation?
It has consequences for any graphical display or statistical test that may be used
How do you calculate mean?
add up all of the values and divide by the number of values
How do you calculate median?
- order values from lowest to highest
- find the middle value
- if there are two middle values, then add them together and divide by two to find the middle value
How do you calculate mode?
- order numbers from either lowest to highest or highest to lowest
- count how many tines each number appears in the set
- the one that appears most is the mode
- there can be more than one mode, or no mode
How do you find the lower quartile, upper quartile and interquartile range
- find the median
- find the median of the first half of the data (Q1)
- find the median of the second half of the data (Q3)
- find the difference between Q3 and Q1 (Q3-Q1)
What are box plots used for?
to show variation within and between data sets
What is an error bar?
a line through a point on a graph, parallel to one of the axes, which represents the uncertainty or variation of the corresponding coordinate of the point
When does correlation exist?
if there is a relationship between two variables
What is the difference between correlation and causation?
correlation is an association and does not imply causation
When does causation exist?
if the changes in the values of the independent variable are known to cause changes to the value of the dependent variable
When does a positive correlation exist?
an increase in one variable is accompanied by an increase in the other variable
