Inference 3

Integrating informed contextual knowledge

• Before you start the investigation, you need to source relevant contextual information which will help you:

• Understand the variables (what they are, what is a normal-range, how they may interact …).

• Generate a purpose for your choice of variables to investigate (Who would want to know and why?).

• Predict what you think you may find, and why.

The hook in could come from:

• Press release• Media clip or interview• Advertisement• Pop quiz based on the topic• …..

Some ideas

• Do girls text more than boys?

• Do Year 13 students spend more at the tuckshop than Year 9 students?

• Do Year 13 students do more homework than Year 9 students?

• State the purpose of your investigation.• Remember to explain why you are investigating

this situation; give a brief background and hypothesis to be investigated. You are expected to do background research to understand the situation.

• Identify the variables you wish to investigate.• Pose an appropriate comparison investigative

question.

Question

• I am interested in investigating whether the average (mean/median) distance driven by males is greater than the average (mean/median) distance driven by females and by how much….

• Level 3 must investigate the “how much”

• Distance driven by females in km• Distance driven by males in km

• This is not sufficient as we are only interested in drivers in NZ in a particular age group.

Excellence

• Can do more comparisons to provide “insight and depth” to your investigation.

• Select and use appropriate displays and statistical measures.

• • Discuss and compare sample distributions

PPDAC CycleUses informed contextual knowledge to support explanations and to communicate findings.

• Makes statistical inferences.• Communicates findings:

– Support (or otherwise) for original hypothesis or conjecture. That is why you need to suggest what you think might happen

– Appropriate graphs that relate to findings discussed in conclusion. Relevant

– Quantifies summary statistics to support (or otherwise) the conjecture.

– Population to which the findings can be generalised. Context– Constraints of the survey within which the findings are valid. Be

specific about the data– Alternative explanations. Investigate more than one reason

Excellence

• Evaluate all stages of the cycle:• Specify, justify, and relate improvements

(contextual or statistical) to the problem

• Note: You can do difference of medians

Think about topics: Time spent in paid employment

• Do people who work longer hours earn more money?