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2 years ago

5.........::.:.:.:.:.:.::::.

Mathematics

1 answer:

Harman [31]2 years ago

4 0

Ok, so first find the cube root of 8.

$- \sqrt [ 3]{8} = - 2$

Now we have:

${3}^{ - 2}$

Which is:

0.11111111111 (1/9)

$answer = d) \: \frac{1}{9}$

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A researcher reports survey results by stating that the standard error of the mean is 25 the population standard deviation is 40

bezimeni [28]

Answer:

a) A sample of 256 was used in this survey.

b) 45.14% probability that the point estimate was within ±15 of the population mean

Step-by-step explanation:

This question is solved using the normal probability distribution and the central limit theorem.

Normal probability distribution

When the distribution is normal, we use the z-score formula.

In a set with mean $\mu$ and standard deviation $\sigma$ , the zscore of a measure X is given by:

$Z = \frac{X - \mu}{\sigma}$

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.

Central Limit Theorem

The Central Limit Theorem estabilishes that, for a normally distributed random variable X, with mean $\mu$ and standard deviation $\sigma$ , the sampling distribution of the sample means with size n can be approximated to a normal distribution with mean $\mu$ and standard deviation $s = \frac{\sigma}{\sqrt{n}}$ .

For a skewed variable, the Central Limit Theorem can also be applied, as long as n is at least 30.

a. How large was the sample used in this survey?

We have that $s = 25, \sigma = 400$ . We want to find n, so:

$s = \frac{\sigma}{\sqrt{n}}$

$25 = \frac{400}{\sqrt{n}}$

$25\sqrt{n} = 400$

$\sqrt{n} = \frac{400}{25}$

$\sqrt{n} = 16$

$(\sqrt{n})^2 = 16^2[tex][tex]n = 256$

A sample of 256 was used in this survey.

b. What is the probability that the point estimate was within ±15 of the population mean?

15 is the bounds with want, 25 is the standard error. So

Z = 15/25 = 0.6 has a pvalue of 0.7257

Z = -15/25 = -0.6 has a pvalue of 0.2743

0.7257 - 0.2743 = 0.4514

45.14% probability that the point estimate was within ±15 of the population mean

3 0

3 years ago

Andycycles7kilometersduringeachtriptowork. HowmanytripswillAndyhavetomaketocycleatotalof21kilometers?

Pie

Andy would have to make 3 trips in order to cycle 21 kilometers.

6 0

3 years ago

Divide 3xsquared - 11x - 4 by x - 4<br><br>a. x+1<br>b. x-23<br>c. 3x+1<br>d. 3x-23

Dmitriy789 [7]

Answer:

c. $3x+1$

Step-by-step explanation:

Since the divisor is in the form of $x - c$ , use what is called Synthetic Division. Remember, in this formula, <em>-c</em> gives you the OPPOSITE terms of what they really are, so do not forget it. Anyway, here is how it is done:

4| 3 −11 −4

↓ 12 4

_______________

3 1 0 → 3x + 1

You start by placing the <em>c</em> in the top left corner, then list all the coefficients of your dividend [3x² - 11x - 4]. You bring down the original term closest to <em>c</em> then begin your multiplication. Now depending on what symbol your result is tells you whether the next step is to subtract or add, then you continue this process starting with multiplication all the way up until you reach the end. Now, when the last term is 0, that means you have no remainder. Finally, your quotient is one degree less than your dividend, so that 3 in your quotient can be a 3x, and the 1 follows right behind it, giving you the quotient of $3x + 1$ .