Question

Scores on a certain exam are normally distributed with a mean of 78 and a variance of 25. What is the z-value for a score of 90?

Answer 1

(Standard Deviation)^2=Variance=25 that means the Standard Deviation = 5
so Z=(x-mean)/Standard Deviation this is the formula you have to memorize it
so Z=(90-78)/5 = 12/5 = 2.4
if you need any more help with Statistics i will be glad to help

Answer 2

thanks, I appreciate it. I need help with this other problem to...

Answer 3

http://www.psychassessment.com.au/pdf/mod2.pdf
Read the above for more insights.

Answer 4

yes sure just post it here :)

Answer 5

thanks eliassaab.

Answer 6

The average length of time between arrivals at a turnpike tollbooth is 23 seconds. Assume that the time between arrivals at the tollbooth is exponentially distributed.
(a) What is the probability that a minute or more will elapse between arrivals?
(b) If a car has just passed through the tollbooth, what is the probability that no car will show up for at least 3 minutes?

Answer 7

ohh :S exponentially distributed ! i have no idea whats that
maybe i forgot it! or we didnt take it yet
sorry

Answer 8

it's all good. yeah, I'm taking business stats. right now.

Answer 9

ohh i took the engineering one so maybe there is a difference or something