HELP ASAP! PLS!! The Water Department checks the city water supply on a regular basis for
contaminants such as lead. The Water Department takes 200 samples and
estimates that the concentration of lead in your drinking water is 3.2 ppb
(parts per billion), with a standard deviation of 0.3 ppb.
Assuming the samples were random and unbiased, how much confidence
can you have in this data?
O
A. 99.7% confident the average concentration of PCBs in the water
supply is between 2.3 ppb and 4.1 ppb.
O
B. 95% confident the average concentration of PCBs in the water
supply is between 2.9 ppb and 3.5 ppb.
O
C. 97% confident the average concentration of PCBs in the water
supply is between 2.6 ppb and 3.8 ppb.
O
D. 68% confident the average concentration of PCBs in the water
supply is between 3.1 ppb and 3.3 ppb.

99.7% confident the average concentration of PCBs in the water supply is between 2.3 parts per billion and 4.1 parts per billion.

Step-by-step explanation:

Just took the question, this is the correct answer.

question 1 is 8, question 2 is 9, question 3 is 24

step-by-step explanation:

now, the numbers they give you at the top are the key. from there, you just have to plug and chug! let's try 1, 2, and 3!

key: a=3, b=5, c=6

1. a+5

remember, a=3, so we plug that in to get 3+5=8

2. 15-c

c=6, so we plug that in to get 15-6=9

3. 4b

b=6, so we plug it in to get 4*6=24

time to try the rest on your own! if you put the answers below in a comment, i'll check them for you!

rick has $1400 and sally has $1500

step-by-step explanation:

to find amount of money rick has after 10 years :

principal = $1000 , time = 10 years , rate = 4% annually

to find amount of money sally has after 10 years :

her friend gives to pay her $50 per year, therefore money she has after 10 years = 50 × 10 = $500

also, sally gets $1000 after 10 years,

therefore, total amount of money sally has after 10 years = 500 + 1000 = $1500

so, after 10 years : rick has $1400 and sally has $1500