Answer:
The 80% confidence interval for the population mean is between 28.32 characters and 31.68 characters.
Step-by-step explanation:
We have the standard deviation for the population, so we can use the normal distribution. If we had the standard deviation for the sample, we would have to use the t-distribution.
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 the margin of error 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 sample mean subtracted by M. So it is 30 - 1.68 = 28.32 characters.
The upper end of the interval is the sample mean added to M. So it is 30 + 1.68 = 31.68 characters.
The 80% confidence interval for the population mean is between 28.32 characters and 31.68 characters.
Answer:
267%
Step-by-step explanation:
you need to divide the second number by the first. This will give you the percentage.
2/3 ÷ 1/4 = 8/3 = 2.67 = 267%
Find factors of 12 and 21
Divide 3 from both numerator and denominator.
(12/21)/(3/3) = 4/7
4/7 is your ratio equivalent to 12/21
hope this helps
Answer:
80 copies
Step-by-step explanation:
4 minutes= 240 seconds. So I did 240 seconds divided by 3 seconds (one copy is made in that time) then you get 80. I don't know if that explanation make sense but the math checks out.
Answer:
7 sides
Step-by-step explanation:
The sum of exterior angles of a polygon is 360°.
Now, exterior angle of the point with interior angle of 120 is; 180 - 120 = 60 (angle on a straight line)
For the others, it is; 180 - 130 = 50
Thus;
60 + 50n = 360
50n = 360 - 60
50n = 300
n = 300/50
n = 6
Thus,number of sides = 6 +1 = 7 sides
