Choosing the Right Procedure

The question the whole exam asks.

12 problems · about 22 minutes · DAT-3.A

What this lesson teaches

The student selects the appropriate inference procedure for a given situation.

Straightforward practice. Get the method working first.

5 problems

Before and after readings on the same people. Which procedure? 1 paired t, 2 two-sample t.
Answer 1
Why A paired t procedure.
What is the first question to ask when choosing a procedure?
Answer Whether the data is counts or measurements.
Why The kind of data.
Before and after measurements on the same subjects. 1 paired t, 2 two-sample t.
Answer 1
Why Natural pairing.
Testing whether two categorical variables are related. 1 chi-square, 2 t-test.
Answer 1
Why Categorical against categorical.
Estimating one population proportion. 1 one-proportion interval, 2 chi-square.
Answer 1
Why One proportion, estimating.

The same ideas with more to keep track of.

3 problems

"Is there evidence" asks for which? 1 interval, 2 test.
Answer 2
Why A decision.
A 3 by 3 table of counts. Degrees of freedom for the chi-square test?
Answer 4
Why (3−1)(3−1).
Is choosing the procedure enough, without checking conditions? 1 yes, 0 no.
Answer 0
Why Conditions carry their own marks.

Mixed problems. Work out what kind of question it is before you start.

4 problems

Sort each situation by the family of procedure it needs.
Answer Mean procedures: Average height of a population, Mean difference before and after · Proportion or chi-square: Percentage supporting a candidate, Counts across four categories
Why Measurements against counts.
Comparing the distribution of one variable across three schools. 1 chi-square, 2 paired t.
Answer 1
Why Several groups, categorical data.
The Choice: Comparing mean commute in two unrelated towns. 1 two-sample t-test, 2 chi-square.
Answer 1
Why A two-sample t-test.
The Estimate: A question asks how much support a candidate has. 1 confidence interval, 2 significance test.
Answer 1
Why A confidence interval.