Choosing the Right Procedure

The question the whole exam asks.

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

NameDate

Figure — use these to answer the problems

Counts in categories point to proportions or chi-square. Measurements point to means.

Category A28

Category B22

Category A28

Category B22

Figure 1

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
2
What is the first question to ask when choosing a procedure?
- Whether the data is counts or measurements.
- How large the sample is.
Before and after measurements on the same subjects. 1 paired t, 2 two-sample t.
Answer
Testing whether two categorical variables are related. 1 chi-square, 2 t-test.
Answer
Estimating one population proportion. 1 one-proportion interval, 2 chi-square.
Answer

The same ideas with more to keep track of.

3 problems

"Is there evidence" asks for which? 1 interval, 2 test.
Answer
A 3 by 3 table of counts. Degrees of freedom for the chi-square test?
Answer
Is choosing the procedure enough, without checking conditions? 1 yes, 0 no.
Answer

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.
Write each item under the heading it belongs to: Average height of a population · Mean difference before and after · Percentage supporting a candidate · Counts across four categories
Mean procedures
Proportion or chi-square
Comparing the distribution of one variable across three schools. 1 chi-square, 2 paired t.
Answer
The Choice
Comparing mean commute in two unrelated towns. 1 two-sample t-test, 2 chi-square.
Answer
The Estimate
A question asks how much support a candidate has. 1 confidence interval, 2 significance test.
Answer