Sampling
Describe how a simple random sample might be taken.
Assign a random number to each member of the population then use a random number generator/pick numbers form a hat to select the sample.
What is a census?
Research that is conducted on the entire population of interest.
What is meant by causation?
A relationship where changes in one variable are the direct cause of changes in another variable.
Sketch the graph of y = -x2 - 1
See board for solution!
What is preface bias?
When a question is preceded by a statement that may influence the response.
What type of study is not affected by lurking variables?
An experimental study.
You send out a survey to collect information for your research. What kind of sample are you collecting by doing this?
Self-selected.
What is a sample?
A group of elements from the population of interest that has been chosen to represent the population.
What is meant by correlation?
An observed association/connection between two variables.
Sketch the graph of y = |x+1| - 3
See the board for solution!
How may systematic sampling produce a biased sample?
If the list of the population follows a pattern e.g. if it lists males and females alternately, then the sample may end up consisting of only one gender.
What is another name for a lurking variable?
A confounding variable.
What is a quota sample?
A sample in which you target a specific characteristic of the population and collect data until you have collected a specific number (quota).
What is a parameter?
A numerical summary (e.g. mean) obtained from the whole population of interest.
What is meant by a biased question?
A question which encourages the respondent to lean towards a specific response.
Sketch the graph of y = (x+1)3 + 5.
See the board for solution!
What makes 'two questions in one' biased?
Respondents may agree with one part and disagree with the other, but they can only give one answer.
What is a lurking variable?
Something which is the true cause behind the behaviours of two variables, and which is responsible for the association observed between them.
What is a stratified sample?
A sample which proportionally represents certain features of the population.
What is a survey?
A set of questions designed to collect information when carrying out research.
What is meant by a biased sample?
A sample that does not fairly represent the population of interest.
Sketch the solution of:
y > (x-2)2
y < |x|
See board for solution!
What is meant by 'biased wording'?
It is the use of positive or negative words in a survey question that can influence a respondent's answer.
In Australia, shark attacks on humans go up with the rate of ice cream sales. Suggest a lurking variable.
Hot weather.
How is a cluster sample collected?
The population of interest is divided into groups (clusters) then a number of these whole groups are randomly selected to create the sample.
What is a statistic?
Numerical summaries (e.g. mean, mode etc) obtained from data collected from a sample.
What is an observational study?
A study which does not impose any kind of change on the sample that is being studied.
Sketch the solution of:
y < (x-2)2
y > |x|
See solution on board!
How can question order lead to bias?
Your answer to the first question may incline you to answer the following question in a specific way.
People taking vitamins are healthier than people who do not take them. Suggest a lurking variable.
Healthy lifestyle.