Studies show that the fuel consumption (mileage) for compacts car sold in Malaysia is normally distributed with a mean 11.5km per liter, with standard deviation 2.2 km/liter. A researcher investigates fuel efficiency of 36 compact cars from various car manufacturers. Find the 90% CI (confidence interval) of the mean, if the investigator found that the mean for 36 samples taken is 13.8 km/liter. Explain the significance of the results.