Cogito
AP Statistics · Chapter 8 · Lesson 3
Communicating Statistical Conclusions
What the exam actually rewards.
12 problems · about 21 minutes · DAT-3.A
What this lesson teaches
The student writes conclusions in context with appropriate justification and hedging.
- Link the p-value to the threshold, state the decision, and answer in context.
- Say evidence, never proof, and fail to reject rather than accept.
- Random sampling permits generalisation; random assignment permits causation.
Warm Up
Straightforward practice. Get the method working first.
5 problemsp-value 0.12 at alpha 0.05. Reject the null? 1 yes, 0 no.
Answer 0
Why No.
Why is "we accept the null" wrong?
Answer Failing to find evidence is not evidence that nothing is there.
Why Absence of evidence is not evidence of absence.
p-value 0.30 at alpha 0.05. Reject the null? 1 yes, 0 no.
Answer 0
Why Above alpha.
Does a statistical test ever prove a claim? 1 yes, 0 no.
Answer 0
Why Evidence, never proof.
What permits generalising to a population? 1 random sampling, 2 random assignment.
Answer 1
Why How subjects were selected.
Build It Up
The same ideas with more to keep track of.
3 problemsWhat permits a causal claim? 1 random sampling, 2 random assignment.
Answer 2
Why How treatments were allocated.
p-value 0.001 at alpha 0.05. Reject? 1 yes, 0 no.
Answer 1
Why Far below alpha.
How many parts does a complete conclusion have: link, decision, context?
Answer 3
Why Count them.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
4 problemsWhich phrases belong in a correct conclusion?
Answer There is convincing evidence that; We fail to reject the null hypothesis
Why Two of these are the phrasings the exam penalises.
p-value 0.049 at alpha 0.05. Reject? 1 yes, 0 no.
Answer 1
Why Just below.
The Decision: p-value 0.02 at alpha 0.05. Reject the null? 1 yes, 0 no.
Answer 1
Why Yes.
The Wording: A large p-value. Do you accept the null? 1 yes, 0 no.
Answer 0
Why No.