# Thread: Statistics Take Home Test Problem

1. ## Statistics Take Home Test Problem

A manufacturer says that not only will 90% of their copiers last at least 36 months, 65% will last at least 42 months. What Normal model parameters is that manufacturer claiming? Show your work.
I have to give it in N(mean, standard deviation).

I don't even know where to start . Maybe I have to compare the percentages and the months to find a standard deviation first but I don't know how to do it.

I'm also confused about the percentages. I understand that it makes logical sense that more copiers would last 36 months than 42 months, but the bell shaped curve works backwards then, since the scale is from lowest to highest and the percentage (based on the z-score) is likewise.

2. Originally Posted by WhoCares357
I don't even know where to start.
If you're trying to anger me, personally, that is an excellent way to start ao conversation. Please start knowing where to start. I just cannot conceive of having no clue at all. Start with breaking out your book. Start with attending class. Start with a table of values for a Standard Normal Distribution. See what I'm saying? You DO have an idea where to start. You just think you are lost when you are not. Fix the attitude problem and you will ahve better success.

Why should anyone help you with a take home test? Shouldn't you show your work? You can't do that if it is someone else's work.

90% at least 36 hours. Find your standard z-score with 90% of the area to the right.

65% at least 42 hours. Find your standard z-score with 65% of the area to the right.

3. Originally Posted by WhoCares357
I have to give it in N(mean, standard deviation).

I don't even know where to start . Maybe I have to compare the percentages and the months to find a standard deviation first but I don't know how to do it.

I'm also confused about the percentages. I understand that it makes logical sense that more copiers would last 36 months than 42 months, but the bell shaped curve works backwards then, since the scale is from lowest to highest and the percentage (based on the z-score) is likewise.