Suppose a radar device tracks the speeds of cars traveling through a city inters

Question

Suppose a radar device tracks the speeds of cars traveling through a city intersection. After recording the speeds of over 10, 000 different cars, local police determine that the speeds of cars through this intersection, in kilometers per hour, follow a normal distribution with a mean mu = 45 and standard deviation sigma = 5. The area under the normal curve between 40 and 50 is equal to 0.68. Select all of the correct interpretations regarding the area under the normal curve. In any sample of cars from this city intersection, 68% travel between 40 and 50 km/h. In the long run, 68% of cars passing through this city intersection travel either 40 or 50 km/h. The probability that a randomly selected car is traveling between 40 and 50 km/h is equal to 0.68. The proportion of cars traveling faster than 40 km/h is equal to 0.68. The long-run proportion of all cars traveling between 40 and 50 km/h is equal to 0.68.

Explanation / Answer

n>10000, we can use nomral distributions

Mean = 45
Standard deviation =5

Area under curve between 40 and 50 is .68

1. False - for samples the deviation is higher. Hencec, making 68% limits higher than 40 and 50
2. False. Its not either 40 or 50. It' between 40 and 50.
3. True. Interpretation in other words
4. False. This would be .68+.16 = .84
5. True.

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