Could someone verify if for the exam we could you the approximation formula present in the booklet, even if the question has less than 20 data points? Would it still be acceptable for exam purposes, the use of the approximate formula? Thanks
Serial correlations test has never been forced upon you in the exam and, where you have the option to avoid it and do a different test, please do. If it gets asked then the formulae given on page 34 of the Tables are sufficient. It is also important to understand what the test achieves and how it is similar to the grouping of signs test in what it is trying to achieve. If the zx values, upon a visual inspection, seemed to have some kind of serial correlation, or there appeared to be too much clumping of the zx's of the same sign then you would be expected to identify this and perform one of these 2 tests. John
