From past results, a professor knows that the test score of a student taking her final examination is a random variable with mean 65 and a variance known to be 15. what is the probability that a student will score between 50 and 80? (7-8.1.2)

(a) somewhere between 0.75 and 0.85
(b) exactly 0.6826
(c) exactly 0.9333
(d) somewhere between 0.55 and 0.75

option B

Step-by-step explanation:

Given,

mean result (μ) = 65

standard deviation (σ)= 15

probability that student will score between 50 and 80

=

=

=

 = P(Z < 1) - P(Z < -1)

Using z table,  

= 0.8413 - 0.1587

= 0.6826

the correct answer is option B

i'm not entirely sure

step-by-step explanation:

if you ask home depot or lowe's they might be able to you out

d

step-by-step explanation:

hello and welcome!

so, when we see the words "proportional" along with a table, we need to know that we're looking numbers that divide by the same thing.

looking at this table, we simply have to do a trial and error, and divide to see which numbers have the same quotient. if you look at choice a & c, they both have equal quotients for three of the numbers, with one exception, so those can't be the answer. looking at b, there is no similarity, so that can't be it. then, we see d; if you divide all the numbers in the table, you'll see that they all divide by two, which is a proportional relationship, and our answer!

also, always remember that the x will always be the number that goes into y, and somewhere behind this table, is a formula. for this specific table, the formula would be:

since our x-value is being divided by two to get the y-value. and if they were to ask for more numbers in the series, this is the formula you would use to find them.