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3 years ago

Va rog sa ma ajutați: 420/180x54/180

2 answers:

4 0

First, you want to divide 420 by 180. Then, divide 54 by 180. Lastly, you want to multiply the answers of the two together.
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420/180= 2.3

54/180= 0.3

2.3 * 0.3 = 0.69

*You just take it step by step. Hope I helped. :)

Sladkaya [172]3 years ago

4 0

Start by simplifying the fractions, its usually easier to leave it as a top heavy fraction. So we would do 420/180 which can be simplified to 7/3 (we can divide both the top and botton of the fraction by 60)
Then we can do 54/180 which is 3/10.
Now we have some nicer fractions all we have to do is multiply 7/3 x 3/10. To do this we can just multiply the tops and bottoms of the fractions so we get 21/30. This can be simplified one last time to get a final answer of 7/10 or 0.7

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Step-by-step explanation:

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2 years ago

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o-na [289]

Answer:

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

And rounded up we have that n=2401

b) $n=\frac{0.07(1-0.07)}{(\frac{0.02}{1.96})^2}=625.22$

And rounded up we have that n=626

And we see that if we have previous info about p the sample size varies a lot.

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:

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

Part a

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)

Since we don't have prior information about the population proportion we can use ase estimator $\hat p =0.5$ . 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

Part b

For thi case the estimator for p is $\hat p =0.07$

$n=\frac{0.07(1-0.07)}{(\frac{0.02}{1.96})^2}=625.22$

And rounded up we have that n=626

And we see that if we have previous info about p the sample size varies a lot.

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3 years ago

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Take the cross product, then normalize the result.

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and so a unit vector orthogonal to both given vectors is

$\dfrac{\mathbf a\times\mathbf b}{\|\mathbf a\times\mathbf b\|}=-\dfrac1{\sqrt2}\,\mathbf i+\dfrac1{\sqrt2}\,\mathbf k$

An equally correct answer would be the negative of this vector, since $\mathbf b\times\mathbf a=-\mathbf a\times\mathbf b$ .

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Answer:

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2 years ago

Read 2 more answers