2026

August 8

1. Aug 8 The overall average hides 8 different numbers Analytics practice
2. Aug 7 A essentially none correlation, and what it is not Statistics
3. Aug 6 What 3,500 job postings say about city Analytics practice
4. Aug 5 Correction: As-of feature computation Machine learning
5. Aug 4 How much statistics do I actually need? Statistics
6. Aug 3 Why there is no analytics on this site Data platform
7. Aug 2 Charting revenue_usd by device Visualization
8. Aug 1 9.9%, plus or minus what? Statistics

July 31

1. Jul 31 A five-minute use for Experiment Calculator Visualization
2. Jul 30 SaaS subscriptions, in one paragraph Data quality
3. Jul 29 Cutting a lesson down — Designing an experiment that can succeed Experimentation
4. Jul 28 How the scheduled posts work Data engineering
5. Jul 27 Pattern: Slowly changing dimension, type 2 Analytics engineering
6. Jul 26 The time coverage of grid-energy-load Data engineering
7. Jul 25 The category that eats the chart Visualization
8. Jul 24 A running total that does not lie about ties Analytics engineering
9. Jul 23 The total came out 8.2× too high Analytics engineering
10. Jul 22 Counting rows is not testing grain Analytics engineering
11. Jul 21 57.8% of churned_at is missing Statistics
12. Jul 20 5,383 zeros in revenue_usd, and what they mean Data quality
13. Jul 19 Before you clip the outliers Statistics
14. Jul 18 The average distance km is not the typical one Statistics
15. Jul 17 Reading reopened before trusting it in support-tickets Data quality
16. Jul 16 Reading 3 columns instead of 12 Data platform
17. Jul 15 gdp_per_capita_usd by region: a 105% spread Analytics practice
18. Jul 14 r = 0.51 between distance_km and tip_usd Statistics
19. Jul 13 Correction: Fan-out join Analytics engineering
20. Jul 12 My experiment came back flat. Now what? Experimentation
21. Jul 11 How scheduled posts work here Data platform
22. Jul 10 Charting baseline_score by arm Visualization
23. Jul 9 The interval is the result Statistics
24. Jul 8 Grid energy load, in one paragraph Data quality
25. Jul 7 What Data Explorer will not do Visualization
26. Jul 6 Cutting a lesson down — The first hour with an unfamiliar dataset Data quality
27. Jul 5 saas-subscriptions.plan: 4 values, 94.0% in the top three Visualization
28. Jul 4 Zero is not a small number Data quality
29. Jul 3 Date spine, in short Analytics engineering
30. Jul 2 posted_on runs 2023-01-01 to 2025-09-27 Data engineering
31. Jul 1 Comparing a period to the one before it Analytics engineering

June 30

1. Jun 30 What wind_mw actually contains in grid-energy-load Data quality
2. Jun 29 The total came out 4.2× too high Analytics engineering
3. Jun 28 Is ticket_id + channel the grain of support-tickets? Analytics engineering
4. Jun 27 21.8% of salary_max_usd is missing Statistics
5. Jun 26 The arithmetic behind a cheap query Data platform
6. Jun 25 The average tip usd is not the typical one Statistics
7. Jun 24 The top of bmi is 1.1× the 99th percentile Statistics
8. Jun 23 revenue_usd by variant: a 48% spread Analytics practice
9. Jun 22 r = 0.14 between load_mw and temp_c Statistics
10. Jun 21 Correction: Gaps and islands Analytics engineering
11. Jun 20 When should I not build a model? Machine learning
12. Jun 19 The build takes under two seconds Data platform
13. Jun 18 Charting flight_no by origin Visualization
14. Jun 17 3.0%, plus or minus what? Statistics
15. Jun 16 If we had to cut the course to ten lessons Experimentation
16. Jun 15 Why Chart Builder works the way it does Visualization
17. Jun 14 Data job postings, in one paragraph Data quality
18. Jun 13 Reader question — Reading a result without fooling yourself Experimentation
19. Jun 12 Deduplicate by rank, in short Analytics engineering
20. Jun 11 The time coverage of sensor-telemetry Data engineering
21. Jun 10 flight-delays.dest: 14 values, 22.3% in the top three Visualization
22. Jun 9 Is posting_id + country the grain of data-job-postings? Analytics engineering
23. Jun 8 A running total that does not lie about ties Analytics engineering
24. Jun 7 The total came out 1.0× too high Analytics engineering
25. Jun 6 What device actually contains in ab-test-checkout Data quality
26. Jun 5 21.8% of salary_min_usd is missing Statistics
27. Jun 4 arr_delay_min: mean 7, median 2 Statistics
28. Jun 3 Zero is not a small number Data quality
29. Jun 2 Reading 3 columns instead of 8 Data platform
30. Jun 1 Before you clip the outliers Statistics

May 31

1. May 31 dep_delay_min by carrier: a 85% spread Analytics practice
2. May 30 A essentially none correlation, and what it is not Statistics
3. May 29 Correction: Idempotent window replace Data engineering
4. May 28 How do I explain a confidence interval to a stakeholder? Statistics
5. May 27 Why the datasets are seeded Data platform
6. May 26 Charting humidity_pct by status Visualization
7. May 25 Zero is not a small number Data quality
8. May 24 42.1%, plus or minus what? Statistics
9. May 23 SQL Playground works offline Visualization
10. May 22 What is deliberately wrong with city-air-quality Data quality
11. May 21 Five minutes with distance_mi in flight-delays Data quality
12. May 20 Reader question — Turning a request into a question Analytics practice
13. May 19 Pattern: Deduplicate by rank Analytics engineering
14. May 18 hour_at runs 2023-01-01 to 2023-12-31 Data engineering
15. May 17 dep_delay_min by origin: a 113% spread Analytics practice
16. May 16 Check the blanks before you drop them Statistics
17. May 15 device_id is not unique, and the join knows Analytics engineering
18. May 14 ab-test-checkout.variant: 3 values, 100.0% in the top three Visualization
19. May 13 A essentially none correlation, and what it is not Statistics
20. May 12 Somebody translated the course into Portuguese Analytics practice
21. May 11 first_response_min: mean 155, median 83 Statistics
22. May 10 Is reading_at + device_id the grain of sensor-telemetry? Analytics engineering
23. May 9 Sessions out of raw events in retail-orders Analytics engineering
24. May 8 Charting sched_dep_hour by origin Visualization
25. May 7 The arithmetic behind a cheap query Data platform
26. May 6 The top of rpm is 1.1× the 99th percentile Statistics
27. May 5 Correction: Deterministic surrogate key Data engineering
28. May 4 The interval is the result Statistics
29. May 3 Is a data engineering certificate worth it? Data engineering
30. May 2 Content is files, not a database Data platform
31. May 1 A five-minute use for Data Explorer Visualization

April 30

1. Apr 30 What is deliberately wrong with flight-delays Data quality
2. Apr 29 Course note — Colour is an encoding, not decoration Visualization
3. Apr 28 Pattern: Baseline before model Machine learning
4. Apr 27 signed_up_on runs 2023-01-04 to 2025-12-01 Data engineering
5. Apr 26 The category that eats the chart Visualization
6. Apr 25 Is subject_id + arm the grain of clinical-trial? Analytics engineering
7. Apr 24 Finding the gaps in ab-test-checkout Analytics engineering
8. Apr 23 user_id is not unique, and the join knows Analytics engineering
9. Apr 22 183 zeros in arr_delay_min, and what they mean Data quality
10. Apr 21 Check the blanks before you drop them Statistics
11. Apr 20 fare_usd: mean 22.16, median 14.29 Statistics
12. Apr 19 Five minutes with year in world-indicators Data quality
13. Apr 18 The arithmetic behind a cheap query Data platform
14. Apr 17 Before you clip the outliers Statistics
15. Apr 16 The overall average hides 4 different numbers Analytics practice
16. Apr 15 A strong correlation, and what it is not Statistics
17. Apr 14 One question I ask in every code review Analytics engineering
18. Apr 13 Correction: Contract check at the boundary Data quality
19. Apr 12 Is my pipeline actually idempotent? Data engineering
20. Apr 11 Charting sched_dep_hour by carrier Visualization
21. Apr 10 What "free" means here, precisely Data platform
22. Apr 9 The interval is the result Statistics
23. Apr 8 The chart rules behind Data Explorer Visualization
24. Apr 7 Flight delays, in one paragraph Data quality
25. Apr 6 Course note — The patterns that keep coming up Analytics engineering
26. Apr 5 The category that eats the chart Visualization
27. Apr 4 Pattern: Conditional pivot Analytics engineering
28. Apr 3 The time coverage of saas-subscriptions Data engineering
29. Apr 2 Comparing a period to the one before it Analytics engineering
30. Apr 1 Zero is not a small number Data quality

March 31

1. Mar 31 The total came out 34.6× too high Analytics engineering
2. Mar 30 Counting rows is not testing grain Analytics engineering
3. Mar 29 The overall average hides 6 different numbers Analytics practice
4. Mar 28 The average sessions is not the typical one Statistics
5. Mar 27 1.6% of pm25 is missing Statistics
6. Mar 26 Five minutes with cancelled in flight-delays Data quality
7. Mar 25 Charting units by country Visualization
8. Mar 24 The arithmetic behind a cheap query Data platform
9. Mar 23 Before you clip the outliers Statistics
10. Mar 22 r = 0.50 between temp_c and solar_mw Statistics
11. Mar 21 The interval is the result Statistics
12. Mar 20 Correction: Forward-chaining split Machine learning
13. Mar 19 Why SQL Playground works the way it does Visualization
14. Mar 18 What is deliberately wrong with saas-subscriptions Data quality
15. Mar 17 Site search without a server, in about 80 lines Visualization
16. Mar 16 retail-orders.category: 6 values, 59.5% in the top three Visualization
17. Mar 15 Course note — A working setup that will not embarrass you Data engineering
18. Mar 14 Merge with a recency guard, in short Data engineering
19. Mar 13 pickup_at runs 2023-01-01 to 2023-12-31 Data engineering
20. Mar 12 Keeping one row per key in retail-orders Analytics engineering
21. Mar 11 Is resolved_at + channel the grain of support-tickets? Analytics engineering
22. Mar 10 Check the blanks before you drop them Statistics
23. Mar 9 gdp_per_capita_usd: mean 26,959, median 20,761 Statistics
24. Mar 8 What salary_max_usd actually contains in data-job-postings Data quality
25. Mar 7 Reading 3 columns instead of 10 Data platform
26. Mar 6 Before you clip the outliers Statistics
27. Mar 5 first_response_min by channel: a 11% spread Analytics practice
28. Mar 4 A essentially none correlation, and what it is not Statistics
29. Mar 3 Correction: The grain uniqueness test Data quality
30. Mar 2 Charting salary_max_usd by seniority Visualization
31. Mar 1 The interval is the result Statistics

February 28

1. Feb 28 A five-minute use for Distribution Lab Visualization
2. Feb 27 What is deliberately wrong with sensor-telemetry Data quality
3. Feb 26 Course note — Joins that do not fan out Analytics engineering
4. Feb 25 Slowly changing dimension, type 2, in short Analytics engineering
5. Feb 24 The time coverage of ab-test-checkout Data engineering
6. Feb 23 Check the blanks before you drop them Statistics
7. Feb 22 The category that eats the chart Visualization
8. Feb 21 Finding the gaps in saas-subscriptions Analytics engineering
9. Feb 20 Is user_id + genre the grain of movie-ratings? Analytics engineering
10. Feb 19 The average arr delay min is not the typical one Statistics
11. Feb 18 Reading borough before trusting it in ride-hail-trips Data quality
12. Feb 17 Reading 3 columns instead of 11 Data platform
13. Feb 16 The top of revenue_usd is 2.8× the 99th percentile Statistics
14. Feb 15 population by country: a 4,739% spread Analytics practice
15. Feb 14 A weak correlation, and what it is not Statistics
16. Feb 13 Correction: Sessionisation Analytics engineering
17. Feb 12 Charting unit_price_usd by channel Visualization
18. Feb 11 2.1%, plus or minus what? Statistics
19. Feb 10 This whole site is 900 lines of Node and one dependency Data engineering
20. Feb 9 A five-minute use for Chart Builder Visualization
21. Feb 8 Deliberately messy customers, in one paragraph Data quality
22. Feb 7 Reader question — When not to build a model Machine learning
23. Feb 6 ride-hail-trips.borough: 5 values, 73.6% in the top three Visualization
24. Feb 5 Idempotent window replace, in short Data engineering
25. Feb 4 The time coverage of city-air-quality Data engineering
26. Feb 3 units: mean 2, median 1 Statistics
27. Feb 2 A running total that does not lie about ties Analytics engineering
28. Feb 1 Is device_id + status the grain of sensor-telemetry? Analytics engineering

January 31

1. Jan 31 2.1% of arr_delay_min is missing Statistics
2. Jan 30 What ordered_at actually contains in retail-orders Data quality
3. Jan 29 The arithmetic behind a cheap query Data platform
4. Jan 28 The top of temp_c is 1.1× the 99th percentile Statistics
5. Jan 27 The overall average hides 30 different numbers Analytics practice
6. Jan 26 r = 0.80 between o3_ppb and temp_c Statistics
7. Jan 25 Correction: Slowly changing dimension, type 2 Analytics engineering
8. Jan 24 Charting csat by channel Visualization
9. Jan 23 A five-minute use for Regression Lab Visualization
10. Jan 22 What is deliberately wrong with retail-orders Data quality
11. Jan 21 Cutting a lesson down — Owning something that runs without you Data platform
12. Jan 20 reading_at runs 2023-01-01 to 2023-02-28 Data engineering
13. Jan 19 Pattern: Deterministic surrogate key Data engineering
14. Jan 18 The category that eats the chart Visualization
15. Jan 17 revenue_usd: mean 111, median 60 Statistics
16. Jan 16 Keeping one row per key in sensor-telemetry Analytics engineering
17. Jan 15 Is ticket_id + queue the grain of support-tickets? Analytics engineering
18. Jan 14 Six things we got wrong, corrected in place Analytics engineering
19. Jan 13 Check the blanks before you drop them Statistics
20. Jan 12 What unit_price_usd actually contains in retail-orders Data quality
21. Jan 11 The arithmetic behind a cheap query Data platform
22. Jan 10 The top of arr_delay_min is 3.1× the 99th percentile Statistics
23. Jan 9 The overall average hides 5 different numbers Analytics practice
24. Jan 8 A essentially none correlation, and what it is not Statistics
25. Jan 7 Correction: Deduplicate by rank Analytics engineering
26. Jan 6 Charting fare_usd by payment_type Visualization
27. Jan 5 A five-minute use for Correlation Explorer Visualization
28. Jan 4 An exercise on clinical-trial Data quality
29. Jan 3 Course note — The five tests that cover most questions Experimentation
30. Jan 2 Forward-chaining split, in short Machine learning
31. Jan 1 flight_date runs 2023-01-01 to 2023-12-31 Data engineering

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