Alimnologist wishes to estimate the mean phosphate content per unit volume of lake water. it is knownfrom studies in previous years that the standard deviation has a fairly stable value ofσ= 4. how manyindependent water samples must the limnologist analyze to be 90% certain that the error of estimation [halfwidth of 90% confidence interval] does not exceed 0.8 milligrams?

68

Step-by-step explanation:

As per given , we have

Population standard deviation :

Critical value for  90% confidence interval =

Margin of error : E= 0.8 milligrams

The formula to find the sample size is given by :-

i.e.

Hence, the limnologist must analyze 68 samples.

to plot points   for x just start at the origin (middle) and go to the left however many times it say(if the number is a positive) if the number is a negative then go right however many times it says if it is 0 go nowhere

now keep you pencil there and go up however many times it says on y(if it is positive) if it is negative then go down however many times it says. if it says 0 go nowhere.

you have just plotted a point! now when you finish plotting all of them connect them with a ruler

plot each point as (-3, 7), (0,4), (3,1), (8,-4)   in the parenthesis on the left of the comma is x and the right is y.

answer: -8.2562234e+13