A researcher at a sleep lab is testing the efficacy of a new sleeping pill. A random sample of 30 people with insomnia is taken from a population of a 100 insomniacs. Given that the mean time it took the 30 subjects to fall asleep is 12.5 min, and that the population standard deviation is 15 min, please construct a 90% confidence interval for the population mean time to fall sleep.
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