A student in a chemistry laboratory measures the rate of a chemical reaction at a fixed temperature across eight trials. She records the following times, in seconds, for the reaction to reach completion:
14.2,11.5,18.9,15.6,12.1,17.4,22.3,15.0 14.2, \quad 11.5, \quad 18.9, \quad 15.6, \quad 12.1, \quad 17.4, \quad 22.3, \quad 15.0 14.2,11.5,18.9,15.6,12.1,17.4,22.3,15.0What is the median time for these trials?
13.9 s13.9\text{ s}13.9 s
14.6 s14.6\text{ s}14.6 s
15.3 s15.3\text{ s}15.3 s
15.9 s15.9\text{ s}15.9 s
44 exam-style questions on OCR GCSE Biology Practical skills. Each one has a worked solution and a mark scheme showing where the marks go.