# Checkpoint assessments

Use closed notes first, then consult the lessons. Each checkpoint has 20 points. Answers and marking criteria are in the separate solutions page. A suggested target is 16/20 on each, followed by correction of every consequential interpretation error. These are proposed instructional thresholds, not validated examinations.

## Checkpoint A After Lesson 4

A1. An order table has 80 orders; an item join has 210 rows. Define both grains and explain which denominator fits “fraction of orders delivered late.” (3 points)

A2. For 2, 3, 4, 5, 16 minutes, calculate mean and median and explain the difference. (3 points)

A3. A graph flags a 90-minute delivery as an outlier. Give two possible explanations and a defensible response. (3 points)

A4. Twenty of 50 customers respond to a survey. Explain why a 40% response rate does not establish representative satisfaction, and name a useful comparison using known data. (4 points)

A5. Distinguish random sampling from random assignment with one consequence of each. (4 points)

A6. Select a chart for distribution of durations and state the horizontal variable, vertical quantity and one chart-design risk. (3 points)

## Checkpoint B After Lesson 8

B1. Out of 1,000 jobs, 50 are delayed. The alert flags 40 delayed and 95 non-delayed jobs. What fraction of flags identify delayed jobs? Explain why 40/50 answers another question. (3 points)

B2. With sample SD 8 and n=64 independent observations, calculate SE and interpret how it differs from SD. (3 points)

B3. Given mean 30, SE 2 and a supplied 95% t multiplier of 2.1, calculate and interpret a mean interval. (4 points)

B4. Explain what a two-sided p-value of 0.03 means under the null model, and give two interpretations it does not support. (4 points)

B5. Explain why a 95% interval spanning −5 to +5 minutes does not establish equivalence between two interventions. (3 points)

B6. A researcher tests 30 outcomes and reports only the smallest p-value. Explain the concern and give one design/reporting improvement. (3 points)

## Checkpoint C After Lesson 11

C1. A rate falls from 10% to 8%. Give the absolute and relative change with correct units. (3 points)

C2. Explain how different route mixtures can reverse an overall hub ranking even if one hub has higher on-time rates within each route type. (3 points)

C3. A regression slope is 1.8 minutes/km. Interpret it descriptively and identify a causal claim it cannot justify on its own. (3 points)

C4. Describe two diagnostic concerns that a high R-squared does not rule out. (3 points)

C5. For the simulated trial's −3.20-minute estimate and [−5.85, −0.55] interval, compare the evidence with zero and a −2-minute worthwhile threshold. Recommend a proportionate next step. (4 points)

C6. Write a two-sentence chart caption for the trial effect, including the contrast, interval meaning, sample size and simulation limitation. (4 points)