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2 years ago

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Mathematics

1 answer:

RSB [31]2 years ago

5 0

Answer:

Step-by-step explanation:

3x² - 3x + 7 = 0

a = 3 ; b = -3 and c = 7

D = b² - 4ac = (-3)² - 4*3*7

D = 9 - 84 = - 75

D = 75i²

√D = √75i² = $\sqrt{5*5*3 * i * i}= 5i\sqrt{3}$

$x = \dfrac{-b+\sqrt{D}}{2a} \ ; \ x=\dfrac{-b-\sqrt{D}}{2a}\\\\ \\x=\dfrac{3+5i\sqrt{3}}{6} ; \ ; x = \dfrac{3-5i\sqrt{3}}{6}\\\\\\x =\dfrac{3}{6}+\dfrac{5i\sqrt{3}}{6} ; \ ; x=\dfrac{3}{6}-\dfrac{5i\sqrt{3}}{6}\\\\\\Solution:\\\\x=\dfrac{1}{2}+\dfrac{5\sqrt{3}}{6}i ; \ ; x=\dfrac{1}{2}-\dfrac{5\sqrt{3}}{6}i$

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a) 0.0885 = 8.85% probability that the mean annual return on common stocks over the next 40 years will exceed 13%.

b) 0.4129 = 41.29% probability that the mean return will be less than 8%

Step-by-step explanation:

To solve this question, we need to understand the normal probability distribution and the central limit theorem.

Normal Probability Distribution:

Problems of normal distributions can be solved using the z-score formula.

In a set with mean $\mu$ and standard deviation $\sigma$ , the z-score 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 p-value, 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.

Mean 8.7% and standard deviation 20.2%.

This means that $\mu = 8.7, \sigma = 20.2$

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This means that $n = 40, s = \frac{20.2}{\sqrt{40}}$

(a) What is the probability (assuming that the past pattern of variation continues) that the mean annual return on common stocks over the next 40 years will exceed 13%?

This is 1 subtracted by the pvalue of Z when X = 13. So

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

By the Central Limit Theorem

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