Question

Hi, I need help with these 8 standard deviation EOC review questions. I need to learn how to do this and also get this assignment turned in ASAP!! Here is the link to the questions, I only need help with 3-10. Thank you so much! ***login link removed***

Answer 1

login required so the link is not appropriate for this site. can you find another way to present them?

Answer 2

yes I can type them in one by one as we work on them. Can you help me?

Answer 3

if i know the questions i can help, standard deviation seems pretty basic if its a starter course.

Answer 4

The shelf life of packaged food follows a normal distribution with a mean of 23 days and a standard deviation of 1.5 days. To the nearest hundredth, what is the probability the packaged food will last for more than 20 days?
Is it:
0.50
0.84
0.95
0.98

Answer 5

ok, we need to measure how many standard deviations it takes to get from the mean to the stated value. (why?)

Answer 6

also, wht do you have to find the value with, ti83? tables? other?

Answer 7

I don't have anything. I would assume I needed to find the z-score and then plug it into an equation. You need to find the distance in order to see if the food can last for more than 20 days? I have no clue I am lost with this.

Answer 8

if you have nothing to calculate with then you are not going to be able to make any feasible calculations. you at least need a table of z values.

stated value - mean gives the distance and direction we need to divide the standard deviation into

20 - 23 = -3

and -3/1.5 = -2 standard deviation from the mean

Answer 9

now what we do with that -2 value, is we would at least look up a table that would give us the appropriate value associated with it.

Answer 10

can you look again and make sure that your course material, or the question itself, has the table as a reference? otherwise we can easily pull it off the google

Answer 11

also a picture of what we are looking for is helpful

mean (middle value of) 23, x value of 20, and we are looking for the stuff that is MORE than 20

Answer 12

now your table needs defined. we have to do some mental gymnastic with what youve given me in order to make the solution work. that involves understanding the mechanics of your table.

are you up to the task?

Answer 13

sure!

Answer 14

notice the first entry: .5000, this tells us that we are measuring left tail areas, and that by starting at the mean, we already have an area of .5000 under our hat.

the more standard deviations we get from the mean, the bigger the area is going to be since we are moving to the right of the mean.

tell me what that tells you so far.

Answer 15

I don't know, the decimal will be a larger number because we are moving to the right?

Answer 16

not knowing is not a good sign

tables by different authors are designed differently.

and each table requires some mental gymnastics in order to use.

your table gives us the area in the left tail of the graph:



as our vale of z gets bigger, we increase in area: