Answer:
The sample mean is
b.3.55
The margin of error is
0.32
Step-by-step explanation:
Deep explanation about a confidence interval
We have that to find our
level, that is the subtraction of 1 by the confidence interval divided by 2. So:

Now, we have to find z in the Ztable as such z has a pvalue of
.
So it is z with a pvalue of
, so 
Now, find M as such

In which
is the standard deviation of the population and n is the size of the sample.

The lower end of the interval is the mean subtracted by M. So it is 6.4 - 0.3944 = 6.01 hours.
The upper end of the interval is the mean added to M. So it is 6.4 + 0.3944 = 6.74 hours.
In this problem:
The deep explanation is not that important.
We just have to recognize that the interval has a lower end and an upper end. The distance from both the upper and the lower end to the mean is M. This means that the sample mean is the halfway point between the lower end and the upper end.
The margin of error is the distance of these two points(lower and upper end) to the mean.
In our interval
Lower end: 3.23
Upper end: 3.87
Sample mean

So the correct answer is:
b.3.55
The margin of error is
3.87 - 3.55 = 3.55 - 3.23 = 0.32
Answer:
Try 458.96 (round if needed)
Step-by-step explanation:
First you find the volume of the cone. (pi*radius^2*h/3)
Then you find the volume of a cylinder. (pi*radius^2*h) add these two up.
You would have to subtract 12.5 and 8.5 to get the height of the cone.
Also you would have to subtract 6 inches off of your total.
(Sorry If this explanation sucked.)
Answer:
B Survey a random sample of eighth-grade students
Step-by-step explanation:
In order to reach the best conclusion without biased data, the best sampling method would be B because not only does it survey 8th graders, but it also surveys a random group, ensuring that not all of the students are potentially excelling in and/or having trouble with homework.