average cost of renting an apartment is $951 with a standard deviation of $96. find the value such that the probability that a randomly selected apartment has a rent of more than it is 0.15

Question

kropot72 · Answer

Look up the standard normal distribution table and find the value of z for a probability (1-.15).

anonymous · Answer

i get a z value of 1.04

kropot72 · Answer

I get a z-score of 1.036 from my table. Can you check again please?

anonymous · Answer

hmm i'm still getting 1.04 for the z-score, because for 1.04 it's .8505, and for 1.03 it's .8485, and my professor told me to choose the one closest to the % we're looking for which in this case is .85

kropot72 · Answer

That's alright. Then substitute the values that you have in the following equation and solve for X.
$$z=\frac{X-\mu}{\sigma}$$

anonymous · Answer

i get $1,050.84

kropot72 · Answer

Great! That is the correct answer :)

anonymous · Answer

sorry to ask, there's just a lot of formulas for different type of probability problems, and i get a bit confused on when to use which. can you maybe explain when to use the formula you listed above?

kropot72 · Answer

|dw:1340481638855:dw|If you do a drawing of the problem it usually helps.