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worty [1.4K]
3 years ago
6

The time spent, in hours, of teenagers on social media per year are normally distributed with a population standard deviation of

442 hours and an unknown population mean. If a random sample of 24 teenagers is taken and results in a sample mean of 1330 hours, find a 99% confidence interval for the population mean.
Mathematics
1 answer:
Olin [163]3 years ago
3 0

Answer:

1329.85≤μ≤1330.14

Step-by-step explanation:

z score for 99% confidence interval

from the z table we can find that the score for 99% confidence is 2.58

formula

z=\frac{x-μ}{[tex]\frac{{σ}[tex]\sqrt{n}}[/tex]}[/tex]

where

x-sample mean

μ-population mean

σ-population standard deviation

n-sample size

2.58=\frac{1330-μ}{[tex]\frac{{442}[tex]\sqrt{24}}[/tex]}[/tex]

1330-2.58×24÷442≤μ≤1330+2.58×24÷442

1329.85≤μ≤1330.14

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A driver is 15 feet below the surface of the water 10 seconds after he entered the water and 90 feet below the surface after 40
spin [16.1K]

Answer:

\frac{-75ft}{30sec} or simplified would be \frac{-2.5ft}{sec}

Step-by-step explanation:

In order to calculate the rate of change, we must subtract his end position and end time by the starting position and starting time. We are using the -15 feet since it is below the surface area as the starting position and the 10 seconds as the starting time. We make each of these into a fraction and subtract like so...

\frac{-90ft - (-15ft)}{40sec - 10sec} = rate of change

\frac{-75ft}{30sec} = rate of change

\frac{-2.5ft}{sec} = rate of change

Therefore, we can see that the rate of change of the diver is \frac{-75ft}{30sec} or simplified would be \frac{-2.5ft}{sec}

6 0
3 years ago
The diameter of a Frisbee is 12 in. What is the area of the Frisbee?
boyakko [2]
The area of the Frisbee is 36π square inches or approximately 113.04 square inches.

Since the Frisbee is circular, its area can be solved by the equation:
A = πr^2 where r= diameter/2 = 6 in
A = 6*6π in
A = 36π square inches or approximately <span>113.04 square inches

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4 0
3 years ago
Whats 6[4x(72-63)÷3]
Minchanka [31]
The answer is 72
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7 0
4 years ago
(I may give brainliest) The roof of a lean-to-garden shed has a gradient of 0.35.find the height?
UkoKoshka [18]

Answer: 2.325 meters

Step-by-step explanation:

The roof of a lean-to-garden shed has a gradient of 0.35.find the height....they have given the base as 1.5m and a shorter height 1.8m its like a house

-------

It sounds like you have a right triangle with base = 1.5,

----

Use a proportion to get:

(height of that triangle)/1.5 = 35/100

height of that triangle = 1.5*0.35 = 0.5250

-----

greater height of the lean-to = 1.8 + 0.5250 = 2.325 meters

3 0
3 years ago
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xxTIMURxx [149]

Answer:


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80 (guards) / 16 (teams) = 5 guards on each team.

6 0
3 years ago
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