The scores on a standardized test are normally distributed with a mean of 80 and standard deviation of 5. What test score is 0.9 standard deviations above the mean?

84.5

Step-by-step explanation:

Given :

Mean μ = 80

Standard deviation, σ = 5

Z = number of standard deviations from the mean, Z = 0.9

Teat score, x

Using the Zscore formula :

Zscore = (x - μ) / σ

Plugging in our values :

0.9 = (x - 80) / 5

Cross multiply

0.9 * 5 = x - 80

4.5 = x - 80

4.5 + 80 = x

x = 84.5

Test score = 84.5

the answer   is 200

step-by-step explanation:

this is a problem about poisson probabilities.   i don't know if you've

already studied poisson distributions, or if you have a place to look

to read more about the subject.  

here's how you can see a poisson distribution coming.   when there are

a lot of events that may happen at any time (or any place), and when

you're counting how many of them happen at a particular time (or a

particular place), and each event is independent of the others, then

the result is a poisson distribution.   this is roughly true for the

chocolate chips; one chip being in a cookie has only a small effect on

the probability that another chip will be in the cookie.

once you know you have a poisson distribution, you know a lot.   there

is only one parameter to a poisson distribution, so if you know the

mean, you know everything.   the form of the distribution is

  probability of n chips = {[e^(-x)]*(x^n)} / (n! )