Question

The weights of cars passing over a bridge have a mean of 3550 lb and a standard deviation of 870 pounds. Assume that the weights of cars passing over the bridge or never distributed. Use the empirical rule to estimate the probability that a randomly-selected car going over the bridge will weigh less than 940 lbs

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Answer 1

a. 0.15%

Explanation:

The Z-score of 940 pounds is ...

(X -µ)/σ = (940 -3550)/870 = -3

The empirical rule tells you that 99.7% of the normal distribution lies within Z = ±3. Half of the remaining 0.3% lies below Z = -3, which is the set of weights of interest.

The probability that a car weighs less than 940 lbs is about 0.15%.