The document discusses principles and best practices for data quality. It outlines key facets of data quality including accuracy, coherence, completeness, consistency, being defined and timely. It provides examples of how to measure these facets through metrics like percentage of records quarantined or missing fields. The document advocates establishing data governance practices like publishing schemas, adhering to definitions, and integrating data quality checks and monitoring into normal workflows. It promotes a culture where data quality is a shared responsibility across teams.

1. Data Quality:
Principles, Approaches, and Best Practices
Carl Anderson
carl.anderson@weightwatchers.com
WW – the new Weight Watchers

2. 1/3 business leaders frequently make
decisions with data they don’t trust
Bad data costs the economy $100s BN / year
[IBM]
[TDWI]

3. Data Science
Business
Intelligence
Engineering
Data Strategy
About Me

5. Big data:
● Food
● Activity
● Exercises
● Challenges
● Social network
● Workshops
● Personal Coaches
● CRM
● Fulfillment
● Meal kits
● Supermarket foods
● E-commerce
● Cruises
...for 56 years

6. 2017: fill lake with data; provide analysts access
2019: upstream control and governance

7. Data Entry Transformation 1 Transformation 2
Inaccurate
(GIGO)
Missing
Defaults
Dropped
records
Truncation
Encoding
changes
Data type
change
Stale
3rd party
Disagree
In General, What Can Go Wrong?
Shape
change
Dupes
Dupes

8. Accurate
Coherent
Complete
Consistent
Defined
Timely
Missing data, duplicates
Referential integrity, connect the dots
Data entry issues, stale data, default dates...
Data dictionaries, business glossary, provenance, schema
Latency
Same values across systems, e.g. same address
Facets of Data Quality
Trust Analysts willing to use data. NPS
*
*
*

9. Accurate
% records quarantined
% records in range
% records matching
Coherent
% records missing entity ID
% records missing foreign key
Complete
% records dupes
% records missing
% records complete
% fields complete
Consistent % records consistent
Defined
% tables defined
% fields defined
% dimensions defined
% measures defined
Timely
Mean time to arrival
95th percentile time to arrival
Volume Number of Records
Trust NPS
“If you can't measure it, you
can't improve it”
- Peter Drucker
Data Quality
Scorecard

10. Facet: Accuracy
Publish Schema Publish Schema
Adhere to Schema
Field Ranges
Source teams then: Source teams now (WIP):
Data team superpowers:
1. Auto consumption
2. Auto checks
3. Quarantine
4. Reporting
Data did not always match schema
Hard to trust
Hard to automate
No accountability

11. Accurate
% records quarantined
% records in range
% records matching
Facet: Accuracy
Publish Schema Publish Schema
Adhere to Schema
Field Ranges
Source teams then: Source teams now (WIP):
Data team superpowers:
1. Auto consumption
2. Auto checks
3. Quarantine
4. Reporting
Data did not always match schema
Hard to trust
Hard to automate
No accountability

12. Facet: Defined
Table-level data dictionaries
Business-level data dictionary
(Business Glossary)
https://medium.com/@leapingllamas

13. Facet: Defined. Flow from master
Data catalog is
master for table-level
definitions and
business glossary
Mapping table from
master to BI tool: here,
Looker dimensions and
measures
Tool compares
master to BI tool and
updates/injects and
creates pull request
Manually
reviewed and
merged
Master definitions
appear to users

14. Facet: Defined. Flow from master
Data catalog is
master for table-level
definitions and
business glossary
Mapping table from
master to BI tool: here,
Looker dimensions and
measures
Tool compares
master to BI tool and
updates/injects and
creates pull request
Manually
reviewed and
merged
Master definitions
appear to users
Open sourcing: https://github.com/ww-tech/lookml-tools

15. Facet: Defined. Style Guide
Open sourcing: https://github.com/ww-tech/lookml-tools
LookML
linter

16. Defined
% tables defined
% fields defined
Facet: Defined
+
LookML
updater
LookML
linter
Defined
% dimensions defined
% measures defined

17. Easy to lose trust. Hard to regain!
We asked:
● NPS data: would you recommend our data to a friend?
● NPS infrastructure: would you recommend our infrastructure (Looker, BigQuery etc) to a friend?
● NPS support: would you recommend CIE’s support to a friend?
We will resurvey at end of 2019
In April, 2019, we surveyed data-related NPS with analysts, data scientists, and
some decisions makers and execs
Trust NPS
Facet: Trust

18. 1 Accurate
% records quarantined
% records in range
% records matching
2 Coherent
% records missing entity ID
% records missing foreign key
3 Complete
% records dupes
% records missing
% records complete
% fields complete
4 Consistent % records consistent
5 Defined
% tables defined
% fields defined
% dimensions defined
% measures defined
6 Timely
Mean time to arrival
95th percentile time to arrival
7 Volume Number of Records
8 Trust NPS
“If you can't measure it, you
can't improve it”
- Peter Drucker
Data Quality
Scorecard
Reference Data
Server logs
Metadata
Schema
Data catalog +
lookml-tools
Survey

19. Integrate into normal workflows
Our engineers work in Slack, so let them do data quality work there too

20. Integrate into team culture
Agile BI engineering team
● BI engineering teams set aside 10% of time for explicit data quality work
● Expect DQ dashboards for all new sources
● Weekly data quality meetings
● Now proactive, rather than reactive or retrospective

21. Data Quality is a Shared Responsibility
Adhere to
Schema
Automated
consumption
DQ Dashboards
Subscribe /
Report
Value Ranges Automated checks
Data
dictionaries
Investigate Investigate
Data dictionaries
+ glossary
Investigate
Single Source of Truth
Investigate
Data Catalog
Data
dictionaries
docsschemaMonitor/
investigate

22. What Questions Do You Have For Me?
Carl Anderson
carl.anderson@weighwatchers.com
@leapingllamas
https://medium.com/ww-tech-blog
We are hiring:
BI engineers, engineers, and data scientists for our Toronto office (a few blocks away).
Find our booth in recruiting hall.