Answer:
The 99% confidence interval for the fraction of U.S. adult Twitter users who get some news on Twitter is between 49.34% and 60.66%, which means that we are 99% sure that the true percentage of US adult Twitter users who get some news is in this interval.
Step-by-step explanation:
Confidence interval:
A confidence interval has the following format:
In which M is the sample mean, z is related to the confidence level and s is the standard error.
55% of U.S. adult Twitter users get at least some news on Twitter (Pew, 2013). The standard error for this estimate was 2.2%.
This means that
99% confidence level
So , z is the value of Z that has a pvalue of , so .
Lower bound of the interval:
Upper bound:
The 99% confidence interval for the fraction of U.S. adult Twitter users who get some news on Twitter is between 49.34% and 60.66%, which means that we are 99% sure that the true percentage of US adult Twitter users who get some news is in this interval.
Answer:
The value of Mary's investment after two years = £12362.7
Step-by-step explanation:
P = Principal / initial amount
R = rate of interest per cent per year
T = number of years
A = final amount at the end of T years
Then:
A = P*(1 + R/100)^2
In our example:
P = £12000
R = 1.5 per cent per year
T = 2 years
Thus:
A = 12000*(1 + 1.5/100)^2
= 12000*(1 + 0.015)^2
= 12000*(1.015)^2
= 12000*(1.030225)
= 12362.7
Value of investment after two years = £12362.7
Answer:
$84 per person because if multiply 84 by 4 its 168
Answer:
C) airplane will land short of the runway by 61 miles
Step-by-step explanation:
the plane is descending 18,000 feet every 50 miles. this means that it wont make it another 50 miles before it hits the ground making C the only possible answer.
We can find this using the formula: L= ∫√1+ (y')² dx
First we want to solve for y by taking the 1/2 power of both sides:
y=(4(x+1)³)^1/2
y=2(x+1)^3/2
Now, we can take the derivative using the chain rule:
y'=3(x+1)^1/2
We can then square this, so it can be plugged directly into the formula:
(y')²=(3√x+1)²
<span>(y')²=9(x+1)
</span>(y')²=9x+9
We can then plug this into the formula:
L= ∫√1+9x+9 dx *I can't type in the bounds directly on the integral, but the upper bound is 1 and the lower bound is 0
L= ∫(9x+10)^1/2 dx *use u-substitution to solve
L= ∫u^1/2 (du/9)
L= 1/9 ∫u^1/2 du
L= 1/9[(2/3)u^3/2]
L= 2/27 [(9x+10)^3/2] *upper bound is 1 and lower bound is 0
L= 2/27 [19^3/2-10^3/2]
L= 2/27 [√6859 - √1000]
L=3.792318765
The length of the curve is 2/27 [√6859 - √1000] or <span>3.792318765 </span>units.