Hi,
In Q5 of the September 2020 CS2 paper A, in the mark scheme for ASET it says we can't use a normal approximation for the binomial as the number of age groups is not sufficiently large. The binomial distribution we're trying to approximate in the Q is Bin(11,0.5), and I thought from CS1 that the test of when we can use a normal approximation for bin(n,p) is as long as n*p is greater than or equal to 5 and n*(1-p) is also greater than or equal to 5. Here n*p = 5.5 and n*(1-p) =5.5 also , so I wasn't sure why this method was not given any marks in the solutions?
Also, in this question the signs test is two-sided, is that always/generally the case for signs tests?
Thanks in advance!
In Q5 of the September 2020 CS2 paper A, in the mark scheme for ASET it says we can't use a normal approximation for the binomial as the number of age groups is not sufficiently large. The binomial distribution we're trying to approximate in the Q is Bin(11,0.5), and I thought from CS1 that the test of when we can use a normal approximation for bin(n,p) is as long as n*p is greater than or equal to 5 and n*(1-p) is also greater than or equal to 5. Here n*p = 5.5 and n*(1-p) =5.5 also , so I wasn't sure why this method was not given any marks in the solutions?
Also, in this question the signs test is two-sided, is that always/generally the case for signs tests?
Thanks in advance!