In a sample with a number n of people surveyed with a probability of a success of $\pi$ , and a confidence level of $1-\alpha$ , we have the following confidence interval of proportions.

$\pi \pm z\sqrt{\frac{\pi(1-\pi)}{n}}$

In which

z is the zscore that has a pvalue of $1 - \frac{\alpha}{2}$ .

The margin of error is:

$M = z\sqrt{\frac{\pi(1-\pi)}{n}}$

95% confidence level

So $\alpha = 0.05$ , z is the value of Z that has a pvalue of $1 - \frac{0.05}{2} = 0.975$ , so $Z = 1.96$ .

At 95% confidence, how large a sample should be taken to obtain a margin of error of 0.03 for the estimation of a population proportion?

We need a sample of n.

n is found when M = 0.03.

We have no prior estimate of $\pi$ , so we use the worst case scenario, which is $\pi = 0.5$

Then

$M = z\sqrt{\frac{\pi(1-\pi)}{n}}$

$0.03 = 1.96\sqrt{\frac{0.5*0.5}{n}}$

$0.03\sqrt{n} = 1.96*0.5$

$\sqrt{n} = \frac{1.96*0.5}{0.03}$

$(\sqrt{n})^{2} = (\frac{1.96*0.5}{0.03})^{2}$

$n = 1067.11$

Rounding up

A sample of 1068 is needed.

8 0

3 years ago

E^x is greater than or equal to 25

kotykmax [81]

Greater than because i honestly don’t know

4 0

3 years ago

What will the temperature be in degrees Fahrenheit when it is 80° Celsius outside? (Recall the formula F = (9C 5) + 32).

xz_007 [3.2K]

The answer is 176 :)

8 0

3 years ago

Read 2 more answers

A survey found that 31% of all teens buy soda (pop) at least once each week. Seven teens are randomly selected. The random varia

kumpel [21]

Answer:

The value of n is 7.

Step-by-step explanation:

For each teen, there are only two possible outcomes. Either they buy soda at least once each week, or they do not. Since they were selected randomly, the teens are independent of each other, which means that we use the binomial probability distribution to solve this question.

Binomial probability distribution

The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.

$P(X = x) = C_{n,x}.p^{x}.(1-p)^{n-x}$

In which $C_{n,x}$ is the number of different combinations of x objects from a set of n elements, given by the following formula.

$C_{n,x} = \frac{n!}{x!(n-x)!}$

And p is the probability of X happening.

In the binomial distribution, we have that n is the size of the sample. In this question, seven teens are randomly selected, which means that the value of n is 7.

7 0

3 years ago