how do i find the percentage and probability of this statistics question???

µ = Mean = 106 min.

σ = Standard Deviation = 8 min.

xbar = 120 min. (2 hours)

……………………

a) Determine the percentage of films that lasted over 2 hours.

z = (xbar – µ) / σ

z = (120 – 106) / 8

z = 14 / 8

z = 1.75

The z-value for 1.75 is 0.4599 (table look up)

The table should be in the appendix of your stats book.

If not, you can view it here:

http://rvgs.k12.va.us/statman/Table-A3.jpg

The probability that a particular film lasted more than 2 hrs.

= 0.5 – 0.4599 = 0.0401

The percentage of films lasting more than 2 hours.

= (0.5 – 0.4599) * 100 = 4.01%

Good luck in your studies,

~ Mitch ~

P.S. – If you have a TI-83 or TI-84,

you can compute this directly on your calculator:

http://www.stat.wmich.edu/s216/book/node49.html

This is a really neat way to save time on tests!