MattEvansC3: "Also that 0.4% failure rate could be higher as there will be a significant number of PS4s that won't be opened until Christmas day."
You might want to refresh that bit about sample sizes from Statistics 101. Even if 90% of those million PS4s are under the tree, the sample size tested would be 100k units, with 400 failures. Even that that gives you high confidence that the failure rate of the full 1M units will be 0.4% to 1 significant figure. (My maths is a bit rusty but I make the 99% confidence interval 0.351 to 0.449).