I've gotten this far on these stat problems but how do i fill in the variable with the probability. formula

1.Replacement times for new Ford Taurus GL automobiles are normally distributed with a mean of 7.1 years and a standard deviation of 1.4 years. Find the probability that seven randomly selected Taurus GL automobiles will have a mean replacement time greater than 7.0 years.


Find the z score for 7 years. (7 - 7.1)/(1.4)

Then look at your z score table, find the area, and subtract from 1. The subtraction is necessary because the table will give you the "less than" probabilities, and you want greater than.

I know this much just need to know how to plug in variables and what the z score is to arrive at the answer.

2) Among U.S. households, 24% have telephone answering machines. If a telemarketing campaign involves 2,500 households, find the probability that more than 650 have answering machines.


2) 24% of 2500 will be 600. The procedure will be the same as for the car, but instead of a standard deviation you'll use an expression that uses the proportion of households .

i recommend that you look at your book and the examples your teachers have given you,
it is an amazing resourse

1. what do you mean - you already plugged in the formulas. 7.-7.1 = -.1
-.1/1.4 = -.071

I don't know what your table looks like, but I think you should end up with an answer of about 52.8%.

Still working on the next one...

Ok is there more info on the next one? Because I can figure out that there is an average of .24 answering machines per household, and that we want to know what the odds are of finding that there are .26 answering machines per household. But in order to calculate this, I need to know how much, on average, every household deviates from the mean. I can't figure this one out, sorry.