A manufacturer claims that 15% of its batteries fail before 500 cycles. A laboratory tests 40 batteries and models the number N N\,N of early failures as binomial.
State the distribution used under the claim.
Find P(N=4)P(N=4)P(N=4).
State two assumptions about the testing needed for the model.
47 exam-style questions on WJEC A Level Maths 2.4 Statistical distributions, covering 2.4.1 Statistical distributions, 2.4.2 Statistical distributions, and 2.4.3 Statistical distributions. Each one has a worked solution and a mark scheme showing where the marks go.