Are you good in statistics subject?

Question

If you're good in statistics, I need your help with my homework.My homework consists of 5 items and I just want an example so that I can work with the others. I was just confused because I just photocopied my homework and forgot to photocopy its examples. So please help me answer the number 1 item.

On Applications of Normal distribution

1. The burning time of an experiment rocket is a random variable which has a normal distribution with a mean of 4.36 seconds and a standard deviation of 0.04 second . What are the probabilities that this kind of rocket will burn for

a. less than 4.25 seconds

b. more than 4.40 seconds

c. 4.30 to 4.42 seconds

Please I need your help in answering this item so I can work with the other 4 items. What formula will I use to solve this? How will I solve this? I am not lazy, I just want a guide so that I can answer the other items. Our teacher did not give us any example that's why I got confused.

Answer 1

You will need to use Tables of the Normal Distribution:

e.g. http://www.math.unb.ca/~knight/utility/N...

Let's us (b) for example:

more than 4.40 sec  -> 0.04 away from mean

-> 1.00 standard deviation

For Row Z=1.0  column 0.00  add up to 1.00 st.dv

The tabulated number = 0.8413, probability < 4.40 sec

So , the answer for (b) 1-0.8413= 0.1587

probability for >4.40sec

As for (a), 4.36-4.25= 0.11 -> 0.275 ST.Dv from mean

(c) just the area between two values.

I believe you can figure out the rest of them.