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Alika [10]
3 years ago
6

K.Brew sells a wide variety of outdoor equipment and clothing. The company sells both through mail order and via the internet. R

andom samples of sales receipts were studied for mail-order sales and internet sales, with the total purchase being recorded for each sale. A random sample of 17 sales receipts for mail-order sales results in a mean sale amount of $82.70 with a standard deviation of $16.25. A random sample of 10 sales receipts for internet sales results in a mean sale amount of $66.90 with a standard deviation of $20.25. Using this data, find the 99% confidence interval for the true mean difference between the mean amount of mail-order purchases and the mean amount of internet purchases. Assume that the population variances are not equal and that the two populations are normally distributed. Step 2 of 3 : Find the margin of error to be used in constructing the confidence interval. Round your answer to six decimal places.
Mathematics
1 answer:
Elan Coil [88]3 years ago
4 0

Answer:

Step-by-step explanation:

The formula for determining the confidence interval for the difference of two population means is expressed as

Confidence interval = (x1 - x2) ± z√(s²/n1 + s2²/n2)

Where

x1 = mean sale amount for mail order sales = 82.70

x2 = mean sale amount for internet sales = 66.9

s1 = sample standard deviation for mail order sales = 16.25

s2 = sample standard deviation for internet sales = 20.25

n1 = number of mail order sales = 17

n2 = number of internet sales = 10

For a 99% confidence interval, we would determine the z score from the t distribution table because the number of samples are small

Degree of freedom =

(n1 - 1) + (n2 - 1) = (17 - 1) + (10 - 1) = 25

z = 2.787

Margin of error =

z√(s²/n1 + s2²/n2) = 2.787√(16.25²/17 + 20.25²/10) = 20.956190

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Can someone please help me in one of these!?
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Answer:

9) y = -200x + 1200

11) slope = -2

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Step-by-step explanation:

9) Given the two points from the graph:

Let (x₁, y₁) = (0, 1200)

(x₂, y₂) =  (1, 1000)

Substitute these values into the following slope formula:

m = (y₂ - y₁)/(x₂ - x₁)

m = (1000 - 1200)/(1 - 0)

m = -200/1

m = -200

The slope of the line is -200.

Next, we need to determine the y-intercept, which is the point on the graph where it crosses the y-axis. Upon observing the graph, it shows that the line crosses at point (0, 1200). The y-coordinate of this ordered pair is the value of the y-intercept, b = 1200.

Therefore, the linear equation in slope-intercept form is y = -200x + 1200.

<h3>11) Given the points, (5, -18) and (-4, 0): </h3>

Let (x₁, y₁) =(5, -18)

(x₂, y₂) =  (-4, 0)

Substitute these values into the following <u>slope formula</u>:

m = (y₂ - y₁)/(x₂ - x₁)

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<h3>15) Solve:</h3>

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We can represent these in slope-intercept form:

y = 150x + 200

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x = number of hours worked.

The y-intercept in this given problem is $200, which represents the flat fee charged for the initial meeting. While the slope in this equation is $150, which is the hourly rate that an Attorney charges his clients after the initial meeting.

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Let x = 15, and substitute its value into the equation to find the total cost:

y = 150x + 200

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<h3>16) Solve: </h3>

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We can establish the following linear equation to model this given problem:

L = -3d + 165

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d = number of days that the water level recedes

In order to find the number of days it will take before the water level recedes to 84 inches:

Substitute the value of L = 84 into the equation:

L = -3d + 165

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Subtract 165 from both sides:

84 - 165 = 3d + 165 - 165

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Divide both sides by  -3:

\frac{-27}{-3} = \frac{-3d}{-3}

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