In: Statistics and Probability
(a) Food Dragon and Delivery Woo are two main food delivery companies in Hong Kong. Suppose the delivery time of these two companies both follow a normal distribution. A random sample of size 10 is selected from each of the food deliveries.
Sample Size mean(mins) standard deviation(mins)
Food Dragon 10 20 5
Delivery Woo 10 15 6
Assuming the delivery times of both companies are normal with equal variances, find the 90% confidence interval for the difference between the mean delivery time of Food Dragon and Delivery Woo. [8marks]
(b) A random sample of 1000 citizens from Macau have been tested for the anti-body for the coronavirus. It was found that 150 of these citizens has the anti-body for the coronavirus. Find a 93% confidence interval for the true population proportion of citizens in the Macau with the anti-body. [5 marks]
(c) An engineer wants to find out the concentration of carbon monoxide (µg/m3 ) emitted by a newly invented car. The engineer collected 14 observations in a randomly chosen period.
68, 54, 32, 80, 50, 40, 60, 60, 55, 40, 42, 50, 60, 43
Construct a 95% confidence interval for the mean concentration of carbon monoxide. Assume that the concentrations of CO are normally distributed. [7 marks]