SOLUTION: Help out cant read z factor The average credit card for college seniors is $4000.If the debt is normally distributed with a standard deviation of $1500, find these probabilities:

Question 1150045: Help out cant read z factor
The average credit card for college seniors is $4000.If the debt is normally distributed with a standard deviation of $1500, find these probabilities:
(a)That the senior owes at least $1000;
stuck at 1-P(Z<-2)
(B)That the senior owes more than $4000;
stuck at 1-P(z<_0)
(c)The senior owes between $3000 and $4000
stuck at P(Z<_0)-P(Z<_-0.666)

Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!

You have the proper z scores for each sub-part. Nice work so far.

To complete the problem, you'll need a z score table (a calculator is another option though it will depend on what your teacher wants). Many, if not all, statistics textbooks will have this table in the back of the book.

I'm using an online z score table found at http://www.z-table.com/ though you can use any table you want, as they would all say the same values.
Here's a portion of the table

Locate the row that starts with -2. I'm going to box it in with red marker

Now highlight the column that has 0.00 at the top

The row -2 and column 0.00 combine to -2+0.00 = -2.00 = -2
In short, this is like an address to find the proper value we want, which is 0.0228

This means P(Z < -2) = 0.0228 approximately

Therefore,
P(Z > -2) = 1 - P(Z < -2)
P(Z > -2) = 1 - 0.0228
P(Z > -2) = 0.9772 which is the final answer to part A (this value is approximate)

I'll let you finish the rest. The other parts follow the same basic steps of using a lookup table to find the proper area, then subtract as you've indicated.
Let me know if you still need help with either part B or part C.
Also, feel free to ask me to check your answers.

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