3. An ambulance agency claims that the mean length of service times is 10 minutes with standard deviation 3 minutes. An investigator suspects that this claim is wrong. She takes a random sample of 20 services and finds the mean length of service times is 12 minutes with a SD 5 minutes. Assume that the service time of the ambulance follows normal distribution. (i) What is the probability that the mean length of service times is less than and equal to 12minutes? (ii) Find 99% confidence interval for standard deviation of the mean length of service times.
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Hypothesis testing: Null hypothesis: The mean length of service times is 10 minutes. Alternative hypothesis: The mean length of service times is greater than 10 minutes. We will use a one-tailed t-test with a significance level of 0.05 and degrees of freedom (df) Show more…
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