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3 years ago

In a study designed to test the effectiveness of acupuncture for treating migraine, 142 subjects

Mathematics

1 answer:

icang [17]3 years ago

6 0

Answer:

Option a) 1.6 .

Step-by-step explanation:

We are given that 142 subjects were treated with acupuncture. The numbers of migraine attacks for the treatment group had a mean of 1.8 and a standard deviation of 1.4 which means;

Sample Mean, $xbar$ = 1.8 , Sample standard deviation, s = 1.4 and Sample size = 142.

Now, 95% confidence interval estimate of the mean number of migraine attacks for all people treated with acupuncture is given by;

$xbar \pm 1.96 *\frac{s}{\sqrt{n} }$

⇒ $1.8 \pm 1.96 *\frac{1.4}{\sqrt{142} }$

So, the lower bound = $1.8 - 1.96 *\frac{1.4}{\sqrt{142} }$ = 1.56 ≈ 1.6

Therefore, option A is correct.

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A Web music store offers two versions of a popular song. The size of the standard version is 2.1 megabytes (MB). The size of the

fiasKO [112]

Answer:

H=310

Step-by-step explanation:

This problem is a great systems of equations problem--you have two different variables: song size and number of songs.

Let's call the number of standard version downloads (S) and the high quality downloads (H).

You can make two statements:

For number of songs downloaded: S + H = 910

For download size: 2.8(S) + 4.4(H) = 3044.

S will be the same number in both equations and H will be the same number in both equations, so to find S, we can rearrange the first statement to H = 910 - S, then substitute or plug in (910 - S) wherever you see an H in the second equation so that you have only S's in your equation. Should look like this:

2.8(S) + 4.4(910 - S) = 3044

2.8S + 4004 - 4.4S = 3044

-1.6S = -960

s = 600

Your question only asks for the standard version downloads, but to help you out in future Systems situations-

You can also solve for H once you have S by plugging it into either of your equations like this:

600 + H = 910

-600

Hope this helps!

7 0

2 years ago

a 9ft ladder is placed 4.5 feet from the base of a wall. How high up will the ladder reach? Round to the nearest hundredth.

spin [16.1K]

Answer:

$\huge\boxed{7.79 \ \text{feet}}$

Step-by-step explanation:

We know that we have a 9 foot long ladder resting upon a wall, with an unknown height, but the ladder is 4.5 feet away from the wall.

This can be represented as a triangle, where x is the unknown side.

| \

x | \ 9

| \

|_____\

4.5

We can use The Pythagorean Theorem to find the value of x. The theorem states that $a^2+b^2=c^2$ , where a and b are the lengths of the legs and c is the length of the hypotenuse.