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andrew11 [14]
3 years ago
14

15 decreased by twice a number

Mathematics
2 answers:
lord [1]3 years ago
7 0

Answer:

15-2x.

Step-by-step explanation:

Let the number be x that needs to be subtracted.

The twice of a number = 2x.

15 is decreased by twice a number

Hence, subtract 2x from 15 i.e, 15-2x

As given according to the question,

The equation will be written as

15-2x

Thus, the answer is 15-2x.

Wewaii [24]3 years ago
4 0
15-2n you are welcome
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Answer:

V=1,244.071

Step-by-step explanation:

I put the answer in decimal form and rounded up from .0706, but pi form in included in the pic. I hope this helped! Please leave Brainliest if it did and is right.

4 0
3 years ago
we believe that 42% of freshmen do not visit their counselors regularly. For this year, you would like to obtain a new sample to
Maksim231197 [3]

Answer:

A sample of 1077 is required.

Step-by-step explanation:

In a sample with a number n of people surveyed with a probability of a success of \pi, and a confidence level of 1-\alpha, we have the following confidence interval of proportions.

\pi \pm z\sqrt{\frac{\pi(1-\pi)}{n}}

In which

z is the zscore that has a pvalue of 1 - \frac{\alpha}{2}.

The margin of error is of:

M = z\sqrt{\frac{\pi(1-\pi)}{n}}

42% of freshmen do not visit their counselors regularly.

This means that \pi = 0.42

98% confidence level

So \alpha = 0.02, z is the value of Z that has a pvalue of 1 - \frac{0.02}{2} = 0.99, so Z = 2.327.

How large of a sample size is required?

A sample size of n is required, and n is found when M = 0.035. So

M = z\sqrt{\frac{\pi(1-\pi)}{n}}

0.035 = 2.327\sqrt{\frac{0.42*0.58}{n}}

0.035\sqrt{n} = 2.327\sqrt{0.42*0.58}

\sqrt{n} = \frac{2.327\sqrt{0.42*0.58}}{0.035}

(\sqrt{n})^2 = (\frac{2.327\sqrt{0.42*0.58}}{0.035})^2

n = 1076.8

Rounding up:

A sample of 1077 is required.

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3 years ago
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What is the square root of 9 2/5 cubed?
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Step-by-step explanation:

7 0
3 years ago
A study was conducted to measure the effectiveness of hypnotism in reducing pain. The measurements are centimeters on a pain sca
saul85 [17]

Answer:

The 95% confidence interval for the difference would be given by (-1.776;0.376)

We are 95% confidence that the true mean difference is between -1.776 \leq \mu_d \leq 0.376. Since the confidence interval contains the value 0, we don't have enough evidence to conclude that hypnotism appear to be effective in reducing pain.

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".

Let put some notation  

x=test value before , y = test value after

x: 6.4 2.6 7.7 10.5 11.7 5.8 4.3 2.8

y: 6.7 2.4 7.4 8.1 8.6 6.4 3.9 2.7

The differences defined as d_i = y_i -x_i and we got:

d: 0.3, -0.2, -0.3, -2.4, -3.1, 0.6, -0.4, -0.1

We can calculate the mean and the deviation for the sample with the following formulas:

\bar d=\frac{\sum_{i=1}^n d_i}{n}

s_d =\frac{\sum_{i=1}^n (d_i -\bar d)^2}{n-1}

\bar d=-0.7 represent the sample mean for the difference

\mu_d population mean (variable of interest)

s_d=1.32 represent the sample standard deviation

n=8 represent the sample size  

Confidence interval

The confidence interval for the mean is given by the following formula:

\bar d \pm t_{\alpha/2} *\frac{s_d}{\sqrt{n}}  (1)

In order to calculate the critical value t we need to find first the degrees of freedom, given by:

df=n-1=8-1=7

Since the Confidence is 0.95 or 95%, the value of alpha=0.05 and \alpha/2 =0.025, and we can use excel, a calculator or a table to find the critical value. The excel command would be: "=-T.INV(0.025,8)".And we see that t_(\alpha/2)=2.306

Now we have everything in order to replace into formula (1):

-0.7-2.306\frac{1.32}{\sqrt{8}}=-1.776    

-0.7+2.306\frac{1.32}{\sqrt{8}}=0.376    

So on this case the 95% confidence interval for the difference would be given by (-1.776;0.376)

We are 95% confidence that the true mean difference is between -1.776 \leq \mu_d \leq 0.376. Since the confidence interval contains the value 0, we don't have enough evidence to conclude that hypnotism appear to be effective in reducing pain.

6 0
3 years ago
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