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:
.005
Step-by-step explanation:
Answer:
3
1
2
Step-by-step explanation:
Step 1: Subtract 9
50.24 = 3.14x²
Step 2: Divide by 3.14
x² = 16
Step 3: Square root both sides
x = ±4
Answer:
Length = 40
Height = 20
Step-by-step explanation:
If you multiply 40 x 20, it equals 800
20 is also half of 40 as well.
By using LCF (Least common factor), the answer would be 24. If you count by sixes and eighteen, the first number they have the same is 24. 6,12,18,24
8,16,24