GEA1000 chap 1 variables, mean, standard deviation, median, interquartile range

bruh im just combining the slides because there's sm shit man

what is a variable

a variable is an attribute that can be measured or labelled

define independent and dependent variables

• IV: an independent variable is a variable that may be subject to manipulation (either deliberately or spontaneously) in a study

• DV: a dependent variable is a variable which is hypothesised to change depending on how the independent variable is manipulated in a study

what are the types of variables that can be used as an IV or DV

• categorical variable

• numerical variable

what is the uses of categorical variables

• take label values

• each observation can be placed in only one label + labels are mutually exclusive

what is the uses of numerical variable

• take numerical values

• and thus arithmetic operations such as adding and averaging make sense

what are the 2 types of categorical variables and their characteristics

• ordinal

  • comes with some natural orderings

  • numbers are often used to represent the ordering (eg mood)

• nominal

  • no intrinsic ordering for their variables (eg types of animals)

what is one thing to note for ordinal categorical variables

differences between numbers are subjective and (may) not be consistent

thus, labelling categories using numbers DOES NOT transform the nature of the variable to become numerical

• calculating averages and performing arithmetic operations is not advisable

what are the 2 types of numerical variables and their characteristis

• discrete

  • possible values of the variable form a set of numbers with ‘gaps’ (eg. no of family members, no of pets in a household)

• continuous

  • can meaningfully take on all possible numerical values in a given range or interval (eg. time)

when should scatter plots be used

to model a relationship between 2 numerical values

when should histograms be used

to show a graph distribution of a single numerical value

when should bar graphs be used

to compare qualities across different categories

when should box plots be used

to compare summary statistics for a numerical variable across different categories

what should be done if the purpose of collecting the data is to get information on particular individuals

go to data set and extract the information for the particular individual(s)

what should be done if the purpose of collecting the data is to get information on groups/population

• data visualisation

• summary statistics

what is a pro and con of data visualisation

+: bring forth patterns which can be used to desc groups of individuals

-: cannot perform calculations → do summary statistics instead

what are the different summary statistics

• measures of central tendency

  • mean

  • median

  • mode

• measures of dispersion

  • standard deviation

  • interquartile range