KEY WORDS

TYPES OF DATA

Data can be

quantitative (numerical data) or

qualitatitive (non-numerical data).

Quantitative data can be

discrete (when it can only take certain values) or

continuous (can take any value in a certain range)

Grouping data

When spread of data is too big we often group the data in a frequency table using class intervals.  Grouping data can result in loss of accuracy in both calculations & presentations.

Bivariate data are used when you measure 2 related things e.g. height & weight of children.

Categorical data is data sorted into categories (groups)

Ranked data have values that can be ranked (put into order)

COLLECTING DATA

Primary data - collected by person who is going to use it.  Not yet been processed. 

Advantages: known accuracy, know how obtained. 

Disadvantages time consuming, expensive.

Secondary data - collected by someone else. 

Advantages cheap & easy to obtain. 

Disadvantages – might be out of date, have mistakes, don’t know how collected.

Experiments – one variable is controlled (explanatory or independent variable) while its effect on the other variable (response or dependent…