Chapter 2 Flashcards
What are types of data?
What is Numerical data?
1/ Numerical (quantitative or interval) data: The values of numerical data are real numbers.
E.g. heights, weights, prices, waiting time at a medical practice, etc.
What is Nominal Data?
2/ Nominal Data (qualitative or categorical): The values of nominal data are categories.
E.g. Responses to questions about marital status are categories, coded as:
Single = 1, Married = 2, Divorced = 3, Widowed = 4
All we can calculate is the proportion of data that falls into each category and the number of observations.
What are Ordinal data?
- *3/ Ordinal (Ranked) Data:**
- *Ordinal data** appear to be categorical in nature, but their values have an order; a ranking to them:
E.g. University course evaluation system:
Poor = 1, fair = 2, good = 3, very good = 4, excellent = 5
While its still not meaningful to do arithmetic on this data (e.g. does 2*fair = very good?!), we can say things like: excellent > poor or fair < very good
Other forms of data
- *1/ Cross-sectional data** is collected at a certain point in time across a number of units of interest.
- Marketing survey (observe preferences by gender, age)
- Students’ marks in a statistics course exam
- *2/ Time-series data** is collected over successive points in time.
- Weekly closing price of gold
- Monthly tourist arrivals in Australia.
What are types of published data?
- *- Primary data
- Secondary data.**
Published data is found as printed material, tapes, disks, and on the Internet which are low cost and convenience.
What is Primary data?
Data published by the organisation that has collected.
E.g. Data published by the Australian Bureau of Statistics
(ABS).
What is Secondary data?
Data published by an organisation different from the one that was originally collected and published it.
E.g. 1. The Yearbook of National Accounts Statistics (United Nations, New York), compiles data from primary sources of various country departments of statistics, like ABS in Australia.
Observational and Experimental data
Observational study: Only observe and do not control any factors that may influence their values.
– e.g. Measuring the height of a tree in the rainforest over time.
Experimental study: Observe and control factors that may influence their values.
– e.g. Measuring the yield of different type of rice using a certain amount of fertilizer (control factor).
What is cencus?
If the data are collected from the whole population, it is called a census.
For example, ABS conducts a census every 5 years in Australia.
Why is a Sampling done more often rather than a Census?
Cost
For example, it’s less expensive to sample 1,000 television viewers than 20 million TV viewers.
Practicality
For example, performing a crash test on every automobile
produced is impractical.
What is Sampling plans?
Sampling plan is just a method or procedure for specifying
how a sample will be taken from a population. Most commonly used sampling plans:
- *- Simple random sampling
- Stratified random sampling
- Cluster sampling.**
How is a sampling size influenced?
The larger the sample size, the more accurate we can
expect the sample estimates to be. Of course, the more costs and time are required.
