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3 years ago

Solve using common logs or natural logs

Mathematics

1 answer:

sesenic [268]3 years ago

5 0

A. x=(In61+2In5)/In5
The answer is: x= 4.55

b. x=(-3In3)/(-2In5+In3)
x=1.55

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Time spent using e-mail per session is normally distributed, with mu equals 11 minutes and sigma equals 3 minutes. Assume that

liq [111]

Answer:

a) 0.259

b) 0.297

c) 0.497

Step-by-step explanation:

To solve this problem, it is important to know the normal probability distribution and the central limit theorem.

Normal probability distribution

Problems of normally distributed samples are solved using 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 random variable X, with mean $\mu$ and standard deviation $\sigma$ , a large sample size can be approximated to a normal distribution with mean $\mu$ and standard deviation $s = \frac{\sigma}{\sqrt{n}}$

In this problem, we have that:

$\mu = 11, \sigma = 3$

a. If you select a random sample of 25 sessions, what is the probability that the sample mean is between 10.8 and 11.2 minutes?

Here we have that $n = 25, s = \frac{3}{\sqrt{25}} = 0.6$

This probability is the pvalue of Z when X = 11.2 subtracted by the pvalue of Z when X = 10.8.

X = 11.2

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

By the Central Limit Theorem

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

$Z = \frac{11.2 - 11}{0.6}$

$Z = 0.33$

$Z = 0.33$ has a pvalue of 0.6293.

X = 10.8

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

$Z = \frac{10.8 - 11}{0.6}$

$Z = -0.33$

$Z = -0.33$ has a pvalue of 0.3707.

0.6293 - 0.3707 = 0.2586

0.259 probability, rounded to three decimal places.

b. If you select a random sample of 25 sessions, what is the probability that the sample mean is between 10.5 and 11 minutes?

Subtraction of the pvalue of Z when X = 11 subtracted by the pvalue of Z when X = 10.5. So

X = 11

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

$Z = \frac{11 - 11}{0.6}$

$Z = 0$

$Z = 0$ has a pvalue of 0.5.

X = 10.5

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

$Z = \frac{10.5 - 11}{0.6}$

$Z = -0.83$

$Z = -0.83$ has a pvalue of 0.2033.

0.5 - 0.2033 = 0.2967

0.297, rounded to three decimal places.

c. If you select a random sample of 100 sessions, what is the probability that the sample mean is between 10.8 and 11.2 minutes?

Here we have that $n = 100, s = \frac{3}{\sqrt{100}} = 0.3$

This probability is the pvalue of Z when X = 11.2 subtracted by the pvalue of Z when X = 10.8.

X = 11.2

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

By the Central Limit Theorem

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

$Z = \frac{11.2 - 11}{0.3}$

$Z = 0.67$

$Z = 0.67$ has a pvalue of 0.7486.

X = 10.8

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

$Z = \frac{10.8 - 11}{0.3}$

$Z = -0.67$

$Z = -0.67$ has a pvalue of 0.2514.

0.7486 - 0.2514 = 0.4972

0.497, rounded to three decimal places.

5 0

3 years ago

Please help with the precalc question above...

Sonja [21]

Answer:

the last choice

Step-by-step explanation:

two functions are said to be inverse when they are symmetric about the line y=x

4 0

3 years ago

When solving the equation x2 – 8x - 7 = 0 by completing the square, which equation

IgorLugansk [536]

<h3>Answer:-</h3>

Lets Solve

$\\ \rm \longmapsto \: {x}^{2} - 8x - 7 = 0 \\ \\ \rm \longmapsto \: {x}^{2} - 8 {}^{}x = 7 \\ \\ \rm \longmapsto \: 4( {x}^{2} - 8x) = 4 \times 7 \\ \\ \rm \longmapsto \: {4x}^{2} - 32x = 28 \\ \\ \rm \longmapsto \: {(2x)}^{2} - 2 \times 2x \times 8 = 28 \\ \\ \rm \longmapsto \: (2x) {}^{2} - 2 \times 2x \times 8 + {8}^{2} = 28 + {8}^{2} \\ \\ \rm \longmapsto \: {(2x - 8)}^{2} = 64 + 28 \\ \\ \rm \longmapsto \: {(2x - 8)}^{2} = 92 \\ \\ \rm \longmapsto \: 2x - 8 = \underline{ + }9.3 \\ \\ \rm \longmapsto \:2x = 8 + 9.3 \: or \: 8 - 9.3 \\ \\ \rm \longmapsto \:2x = 17.3 \:or \: - 1.3 \\ \\ \rm \longmapsto \:2x = 17.3 \\ \\ \rm \longmapsto \:x = \frac{17.3}{2} \\ \\ \rm \longmapsto x = \:8.6$