82The Ratio Scale•The ratio scale represents the strongest level of measurement. •Ratio data have all the characteristics of interval data as well as a true zero point, which allows us to interpret the ratios of values.
83Scales of Measure
84Variable Types •Time Series and Cross-Sectional Data •Variables that are measured at regular intervals over time are called time series. •For example, the share price of the Royal Bank of Canada at the end of each day for the past year.
85Time series data•Data collected by recording a characteristic of a subject over several time periods.•Data can include daily, weekly, monthly, quarterly, or annual observations.•This graph plots the U.S. GDP growth rate from 1980 to 2010 - it is an example of time series data.
86Variable Types •Time Series and Cross-Sectional Data •When several variables are all measured at the same point in time, the data is called cross-sectional data.•For example, collecting data on sales revenue, number of customers, and expenses totalled over the past month at each Starbucks location.
87Cross-sectional data•Data collected by recording a characteristic of many subjects at the same point in time, or without regard to differences in time.•Subjects might include individuals, households, firms, industries, regions, and countries.•The survey data from the Introductory Case is an example of cross-sectional data.
89Variable Types •Primary and Secondary Data •Primary data are data we collect ourselves and that the researchers have a very clear idea of the meaning of the data they collect from surveys, since they themselves design the wording of every question in those surveys and conduct the interviews.
90Variable Types •Primary and Secondary Data •Secondary data are data collected by another party, like Statistics Canada. It is very important to read all the guidelines and footnotes provided in order to get a precise idea of what the secondary data mean.