X 2 + 6x + 8 = 0 Final answer: x = x = ___

Sample size: A researcher is trying to decide how many people to survey. Which of the following sample sizes will result in a co

oksian1 [2.3K]

Answer:

Step-by-step explanation:

Given that a researcher is trying to decide how many people to survey.

We have confidence intervals are intervals with middle value as the mean and on either side margin of error.

Confidence interval = Mean ± Margin of error

Thus confidence interval width depends on margin of error.

Margin of error = $Critical value *\frac{\sigma}{\sqrt{n} }$

Thus for the same confidence level and std deviation we find margin of error is inversely proportional to square root of sample size.

Hence for small n we get wide intervals.

So if sample size = 300, the researcher will get wider confidence interval

4 0

3 years ago

Find the equation of a line that passes through the point (3,1) and has a gradient of -3. Leave your answer in the form y = m x

Bingel [31]

Answer:

$y = (-3)\, x + 10$ .

Step-by-step explanation:

The question requires that the equation should be in the slope-intercept form $y = m \, x + c$ . The $m$ and $c$ in this equation are constants. In particular:

$m\!$ would represent the slope of this line (also known as the gradient of this line,) whereas
$c$ would be the $y$ -intercept of this line.

The question states that the slope of this line is $(-3)$ . Therefore, $m = -3$ . Thus, the equation for this line should be in the form $y = (-3)\, x + c$ .

The value of constant $c$ could be found using the other piece of information: the point $(3,\, 1)$ is in this line. In other words, the solution $\text{$x = 3$ and $y = 1$}$ should satisfy the equation $y = (-3)\, x + c$ .

Substitute $\text{$x = 3$ and $y = 1$}$ into the equation $y = (-3)\, x + c$ and solve for $c$ :

$1 = (-3) \times 3 + c$ .

$1 = -9 + c$ .

$c = 10$ .

Hence, $y = (-3) \, x + 10$ would be the slope-intercept form of the equation of this line.

3 0

2 years ago

An HP laser printer is advertised to print text documents at a speed of 18 ppm (pages per minute). The manufacturer tells you th

aliya0001 [1]

Answer:

0.227 = 22.7% probability that the mean printing speed of the sample is greater than 18.12 ppm.

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