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Tony Hoare's InfoQ talk in which he describes introducing null references in ALGOL W in 1965 and calls it his billion-dollar mistake. He discusses language designer responsibility and run-time checks.

Sandi Metz argues that hidden assumptions in code are missing concepts, and shows how to name and expose them so code is easier to understand and change. It covers null objects and messages in Ruby.

Stuart Marks explains the intended purpose and proper use of Java 8's Optional class and why it caused so much controversy. He gives guidelines for using its small API correctly.

Geoff Cumming uses a simulation to show how wildly the p value varies from one replication to the next because of sampling variability. He argues for estimation and confidence intervals over null hypothesis significance testing.