Solutions

An electronic device is advertised as being able to retain information stored in it for at least 80 hours after power has been switched off. In experiments carried out to test this claim, the retention time in hours, X, was measured on 250 occasions, and the data obtained is summarized by E(x-76) =683, E(x-76)? = 26 132. (i) Calculate unbiased estimates of the population mean and variance of the retention time. [2] (ii) Test, at the 5% significance level, whether there is any evidence to doubt the claim. [5] (iii) Explain, in the context of the question, the meaning of "at the 5% significance level". [1] (iv) Find the smallest level of significance at which the test would result in rejection of the null hypothesis. [3]An electronic device is advertised as being able to retain information stored in it for at least 80 hours after power has been switched off. In experiments carried out to test this claim, the retention time in hours, X, was measured on 250 occasions, and the data obtained is summarized by E(x-76) =683, E(x-76)? = 26 132. (i) Calculate unbiased estimates of the population mean and variance of the retention time. [2] (ii) Test, at the 5% significance level, whether there is any evidence to doubt the claim. [5] (iii) Explain, in the context of the question, the meaning of "at the 5% significance level". [1] (iv) Find the smallest level of significance at which the test would result in rejection of the null hypothesis. [3]