Can someone please help me and write out the answer

The weekly earnings of students in one age group are normally distributed with a standard deviation of 47 dollars. A researcher

ELEN [110]

Answer:

Option D) 340

Step-by-step explanation:

We are given the following in the question:

Alpha, α = 0.05

Population standard deviation, σ = $47

Margin of error = 5

95% Confidence Interval:

$\mu \pm z_{critical}\frac{\sigma}{\sqrt{n}}$

$\text{Margin of error} = z_{critical}\frac{\sigma}{\sqrt{n}}$

Putting the values, we get,

$z_{critical}\text{ at}~\alpha_{0.05} = 1.96$

$5 = 1.96(\dfrac{47}{\sqrt{n}} )\\\\\sqrt{n} = \dfrac{47\times 1.96}{5}\\\\n = 339.443776\\\Rightarrow n \approx 340$

Thus, the correct answer is

Option D) 340

7 0

3 years ago

the runner's time to complete the marathon is 45 minutes. The time to complete the last marathon was 49.5 minutes. What is the p

Lana71 [14]

Answer:

9.09%

Step-by-step explanation:

To find percent decrease you have to use this equation:

$Percent Decrease = \frac{Initial -New}{Initial} x 100$

Initial = 49.5

New = 45

Plug in and solve:

$PD = \frac{49.5-45}{49.5} x 100\\\\PD = \frac{4.5}{49.5} x 100 \\\\PD = 0.0909 x 100\\\\PD = 9.09$

The percent decrease is 9.09%

<em>Hope this helps!!</em>

6 0

3 years ago

The circumference of Tyler's bike tire is 72 inches. What is the diameter of the tire?

pantera1 [17]

Answer:

The diameter is 22.92 inches

Step-by-step explanation:

Hello, I can help you with this question

in this case we know the circumference of a circle, and we need to find out the diameter.

let's remember

the radius of a circle can be defined as

$radius=\frac{diameter}{2}\\ or\\diameter=2* radius( equation\ 1)\\$

also

$circumference=2*\pi *radius(equation2)\\$

Step1

replace the value of the circumference of tyler's bike in equation 2 and isolate radius to find radius

$72 inches=2*\pi *radius\\\\radius=\frac{72}{2*\pi } \radius =11.46\ inches$

Step 2

now, replace the value of radius into equation 1 to find diameter

radius=11.46 in

$diameter=2* radius( equation\ 1)\\\\diameter=2*11.46\\diameter=22.92$

so, the diameter is 22.92 inches

I really hope it helps, have a great day.

5 0

3 years ago

Read 2 more answers

Copy and complete the statement using <,>,= |-11 |-10|

EleoNora [17]

|-11| > |-10|
this is because the absolute value is always a positive number. therefore, it is really 11 > 10.

6 0

3 years ago

Read 2 more answers

Which expression is equivalent to (r Superscript negative 7 Baseline) Superscript 6? r Superscript 42 StartFraction 1 Over r Sup

vodomira [7]

Power rule of exponents says that the power of the power of a exponent is equal to the multiplying both the powers. The expression which is equal to the given expression is,

$\dfrac{1}{(r)^{42}}$

The option B is the correct option.

Given information-

The given expression in the problem is,

$[(r)^{-7}]^5$

<h3>Power rule of exponents</h3>

Power rule of exponents says that the power of the power of a exponent is equal to the multiplying both the powers.

Suppose<em> </em><em>x</em> is a number with power <em>a. </em>The power is power of the power of number <em>x. </em>Then by the power rule of the exponents,

$(x^a)^b=x^{ab}$

Using the power rule of the exponents given expression can be written as,

$[(r)^{-7}]^6=(r)^{-7\times 6} 
$

$[(r)^{-7}]^6=(r)^{-42}$

<h3>Negative exponents rule</h3>

Negative exponents rule says that when a power of a number is negative, then write the number in the denominator with the same power with positive sign.Thus,

$[(r)^{-7}]^6=\dfrac{1}{(r)^{42}}$

Hence the expression which is equal to the given expression is,

$\dfrac{1}{(r)^{42}}$

The option B is the correct option.

Learn more about the power rule of exponents here;

brainly.com/question/819893

8 0

2 years ago

Read 2 more answers

Can someone please help me and write out the answer​

Can someone please help me and write out the answer