The time, in seconds, taken for a automated process to complete is normally distributed with a mean of 120 seconds and a standard deviation of 10 seconds. An engineer monitors a process run.
Find the probability that the process takes longer than 110 seconds.
The process has already been running for 110 seconds. Find the probability that it runs for another 20 seconds.
The engineer believes that the mean completion time for these processes is longer than 120 seconds. She records a random sample of 25 process runs and found that their mean time was 122 seconds. Stating your hypotheses clearly and using a 5% level of significance, test the engineer's belief.
284 exam-style questions on CCEA A Level Maths 4.5 Statistical distributions (A-level only), covering 4.5.1 Statistical distributions (A-level only) and 4.5.2 Statistical distributions (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.