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alina1380 [7]
3 years ago
9

Denise is a professional swimmer who trains, in part, by running. she would like to estimate the average number of miles she run

s in each week. for a random sample of 20 weeks, the mean is = 17.5 miles with standard deviation s = 3.8 miles. find a 99% confidence interval for the population mean number of miles denise runs. use a graphing calculator for this one and not the t chart from the book.
Mathematics
1 answer:
SSSSS [86.1K]3 years ago
4 0
Given:
n = 20, sample size
xbar = 17.5, sample mean
s = 3.8, sample standard deiation
99% confidence interval

The degrees of freedom is 
df = n-1 = 19

We do not know the population standard deviation, so we should determine t* that corresponds to df = 19.
From a one-tailed distribution, 99% CI means using a p-value of 0.005.
Obtain
t* = 2.8609.

The 99% confidence interval is
xbar +/- t*(s/√n)

t*(s/√n) = 2.8609*(3.8/√20) = 2.4309
The 99% confidence interval is
(17.5 - 2.4309, 17.5 + 2.4309) = (15.069, 19.931)

Answer: The 99% confidence interval is (15.07, 19.93)
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The variance of a distribution is 195. What is the standard deviation, rounded to the nearest thousandth?
stiks02 [169]

Given:

The variance of a distribution = 195.

To find:

The standard deviation, rounded to the nearest thousandth.

Solution:

Standard deviation of a distribution is the square root of the variance of the distribution.

Here, the standard deviation of the distribution is

S.D.=\sqrt{195}

S.D.=13.96424

S.D.\approx 13.964

Therefore, the standard deviation is 13.964.

8 0
3 years ago
If you are offered one slice from a round pizza (in other words, a sector of a circle) and the slice must have a perimeter of 24
VARVARA [1.3K]

Answer:

A 12 in diameter will reward you with the largest slice of pizza.

Step-by-step explanation:

Let r be the radius and \theta be the angle of a circle.

According with the graph, the area of the sector is given by

A=\frac{1}{2}r^2\theta

The arc lenght of a circle with radius r and angle \theta is r \theta

The perimeter of the pizza slice is composed of two straight pieces, each of length r inches, and an arc of the circle which you know has length s = rθ inches. Thus the perimeter has length

2r+r\theta=24 \:in

We need to express the area as a function of one variable, to do this we use the above equation and we solve for \theta

2r+r\theta=24\\r\theta=24-2r\\\theta=\frac{24-2r}{r}

Next, we substitute this equation into the area equation

A=\frac{1}{2}r^2(\frac{24-2r}{r})\\A=\frac{1}{2}r(24-2r)\\A=12r-r^2

The domain of the area is

0

To find the diameter of pizza that will reward you with the largest slice you need to find the derivative of the area and set it equal to zero to find the critical points.

\frac{d}{dr} A=\frac{d}{dr}(12r-r^2)\\A'(r)=\frac{d}{dr}(12r)-\frac{d}{dr}(r^2)\\A'(r)=12-2r

12-2r=0\\-2r=-12\\\frac{-2r}{-2}=\frac{-12}{-2}\\r=6

To check if r=6 is a maximum we use the Second Derivative test

if f'(c)=0 and f''(c), then f(x) has a local maximum at x = c.

The second derivative is

\frac{d}{dr} A'(r)=\frac{d}{dr} (12-2r)\\A''(r)=-2

Because A''(r)=-2 the largest slice is when r = 6 in.

The diameter of the pizza is given by

D=2r=2\cdot 6=12 \:in

A 12 in diameter will reward you with the largest slice of pizza.

3 0
3 years ago
What factors of 32 add up to -12
irakobra [83]

Answer: -8 and -4

This is something you do through trial and error. Making a list or a table like shown below might help.

8 0
3 years ago
What is the equation of the line that passes through the point (-8,2) and had an undefined slope
Basile [38]

Answer:

-8..hope it helps you

Step-by-step explanation:

x=-8..Y=2

5 0
3 years ago
Bernice wants to buy two
Olegator [25]

Answer:

$3.72

Step-by-step explanation:

7.75*2=15.5

15.5+0.78=16.28

20-16.28=3.72

3 0
2 years ago
Read 2 more answers
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