Data Quality: principles, approaches, and best practices
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.
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 lakewith data; provide analysts access
2019: upstream control and governance
7.
Data Entry Transformation1 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
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 SchemaPublish 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 datadictionaries
Business-level data dictionary
(Business Glossary)
https://medium.com/@leapingllamas
13.
Facet: Defined. Flowfrom 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. Flowfrom 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. StyleGuide
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 losetrust. 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
% recordsquarantined
% 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 normalworkflows
Our engineers work in Slack, so let them do data quality work there too
20.
Integrate into teamculture
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 isa 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 DoYou 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.