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Damm [24]
3 years ago
8

g A researcher wants to construct a 95% confidence interval for the proportion of children aged 8-10 living in Atlanta who own a

cell phone. Estimate the sample size needed if no estimate of p is available so that the confidence interval will have a margin of error of 0.02.
Mathematics
2 answers:
hodyreva [135]3 years ago
8 0

Answer:

n=\frac{0.5(1-0.5)}{(\frac{0.02}{1.96})^2}=2401  

And rounded up we have that n=2401

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 95% of confidence, our significance level would be given by \alpha=1-0.95=0.05 and \alpha/2 =0.025. And the critical value would be given by:

z_{\alpha/2}=-1.96, z_{1-\alpha/2}=1.96

The margin of error for the proportion interval is given by this formula:  

ME=z_{\alpha/2}\sqrt{\frac{\hat p (1-\hat p)}{n}}    (a)  

And on this case we have that ME =\pm 0.02 and we are interested in order to find the value of n, if we solve n from equation (a) we got:  

n=\frac{\hat p (1-\hat p)}{(\frac{ME}{z})^2}   (b)  

For this case we can use an estimator for the population proportion as \hat p = 0.5. And replacing into equation (b) the values from part a we got:

n=\frac{0.5(1-0.5)}{(\frac{0.02}{1.96})^2}=2401  

And rounded up we have that n=2401

Helga [31]3 years ago
7 0

Answer:

The sample size needed is 2401.

Step-by-step explanation:

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 of the interval 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.

Estimate the sample size needed if no estimate of p is available so that the confidence interval will have a margin of error of 0.02.

We have to find n, for which M = 0.02.

There is no estimate of p available, so we use \pi = 0.5

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

0.02 = 1.96\sqrt{\frac{0.5*0.5}{n}}

0.02\sqrt{n} = 1.96*0.5

\sqrt{n} = \frac{1.96*0.5}{0.02}

(\sqrt{n})^{2} = (\frac{1.96*0.5}{0.02})^{2}

n = 2401

The sample size needed is 2401.

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Step-by-step explanation:

29 ÷ 8 = 3 remainder: 5

I solved using long division.

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Karolina [17]

Please consider the attached file.

We can see that triangle JKM is a right triangle, with right angle at M. Segment KM is 6 units and segment MJ is 3 units. We can also see that KJ is hypotenuse of right triangle.

We will use Pythagoras theorem to solve for KJ as:

KJ^2=KM^2+MJ^2

KJ^2=6^2+3^2

KJ^2=36+9

KJ^2=45

Now we will take positive square root on both sides:

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KJ=3\sqrt{5}

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5 0
3 years ago
Round each number to the nearest hundred and estimate the sum. 1,382 + 966
Daniel [21]

Answer:

1,500

Step-by-step explanation:

1,382 + 966

Rounding to the nearest hundred would be:

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8 0
2 years ago
For which color is the difference between the theorectical probability and experimental probability greatest?
Elan Coil [88]

Answer:

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5 0
3 years ago
A baseball is hit into the​ air, and its height h in feet after t seconds is given by h(t)= -16t^2+128t+2. The height of the bas
tankabanditka [31]

Answer:

\large \boxed{\sf \ \text{2 feet, 4 seconds, 258 feet } \ }

Step-by-step explanation:

Hello,

To know the height of the baseball when it is hit we have to compute h(0), as t = 0 is when the baseball is hit into the air.

h(0)=-16\cdot 0^2+128 \cdot 0+2=2

So, the answer is <u>2 feet.</u>

<u />

h(x) is a parabola which can be written as ax^2+bx+c, it means that the vertex is the point (-b/2a,h(-b/2a)).

The baseball reached its maximum height after

   \dfrac{-b}{2a}=\dfrac{-128}{-2*16}=\boxed{4 \text{  seconds}}

And the maximum height of the baseball is h(4).

h(0)=-16\cdot 4^2+128 \cdot 4+2=-256+512+2=\boxed{258 \ \text{feet}}

Hope this helps.

Do not hesitate if you need further explanation.

Thank you

8 0
3 years ago
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