I am struggling with understanding probabilities: Did I calculate this correctly. Can you help with the explanation?

The probability is 1 in 4,000,000 that a single auto trip in the United States will result in a fatality. Over a lifetime, an average U.S. driver takes 50,000 trips. (a) What is the probability of a fatal accident over a lifetime? Explain your reasoning carefully. Hint: Assume independent events. Why might the assumption of independence be violated? (b) Why might a driver be tempted not to use a seat belt “just on this trip”?

(a) – 1 / 4,000,000 = .0000002 x 50,000 = .01 or 1% probability

A driver might be tempted not to use the seat belt ‘just on this trip” because the probability is so low versus how many trips he/she will make in a lifetime.

How might independence be violated? - the way I see it it is that you either die or not therefore it has to remain independent - doesn't it?

Well done here also jane! You're progressing! :)

Can this problem be answered using Excel? If so, how?

Hum, for that, I don't know... sorry... :( But surely, someone will tell you later, when that someone will find the post.