Answer:
And rounded up we have that n=99
Step-by-step explanation:
Previous concepts
A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".
The margin of error is the range of values below and above the sample statistic in a confidence interval.
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
Solution to the problem
In order to find the critical value we need to take in count that we are finding the interval for a proportion, so on this case we need to use the z distribution. Since our interval is at 99% of confidence, our significance level would be given by
and
. And the critical value would be given by:
The margin of error for the proportion interval is given by this formula:
(a)
And on this case we have that
and we are interested in order to find the value of n, if we solve n from equation (a) we got:
(b)
We assume the value for
since we don't have previous info. And replacing into equation (b) the values from part a we got:
And rounded up we have that n=99
a+b+c=68
b-3=a
c-5=b
now just solve the system of equations, substitue so that there are only b's in the equation:
a+b+c=68
(b-3) + b + (b+5) = 68
3b=66
b=22
Therefore Barbara is 22
I hope it helps, let me know if it’s right
Answer:
11.2
Step-by-step explanation:
If the rectangulars are similar then we can use similarity ratio to calculate value of x
CD is similar to RS and AB is similar to QP
4/6.4 = 7/x cross multiply expressions
4x = 44.8 divide both sides by 4
x = 11.2
Answer: i think its the 3rd one
Step-by-step explanation: