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Nookie1986 [14]
3 years ago
15

In order to officailly bid on a contract, a contractor wants to be 95% confident that his error is less than two hours in estima

ting the average time it takes to install tile flooring. Previous contracts indicate that the standard deviation is 4.5 hours. How large a sample must be selected?
Mathematics
1 answer:
iVinArrow [24]3 years ago
4 0

Answer: 20

Step-by-step explanation:

Formula to find the sample size : n=(\dfrac{\sigma\times z_{\alpha/2}}{E})^2

Given : Significance level : \alpha=1-0.95=0.05

Critical value : z_{\alpha/2}=1.96

Margin of error : E

Standard deviation: \sigma=\text{ 4.5 hours}

Then, we have

n=(\dfrac{4.5\times(1.96)}{2})^2=19.4481\approx20

Hence, the minimum sample size must be 20.

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netineya [11]
About 224.7 I think. I hope this helps
7 0
2 years ago
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The vector ab has a magnitude of 20 units and is parallel to the<br> vector 4i + 3j.<br> find ab.
stepladder [879]

The vector ab has a magnitude of 20 units and is parallel to the

vector 4i + 3j. Hence, The vector AB is 16i + 12j.

<h3>How to find the vector?</h3>

If we have given a vector v of initial point A and terminal point B

v = ai + bj

then the components form as;

AB = xi + yj

Here, xi and yj are the components of the vector.

Given;

The vector ab has a magnitude of 20 units and is parallel to the

vector 4i + 3j.

magnitude

\sqrt{4^2 + 3^2} \\\\\sqrt{16 + 9} \\\\= 5

Unit vector in direction of resultant = (4i + 3j) / 5

Vector of magnitude 20 unit in direction of the resultant

= 20  x (4i + 3j) / 5

= 4 x (4i + 3j)

= 16i + 12j

Hence, The vector AB is 16i + 12j.

Learn more about vectors;

brainly.com/question/12500691

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7 0
1 year ago
Assume a gasoline price of $3.55 per gallon. What is the gasoline cost for a 2000 mile trip if you drive at an average speed of
saul85 [17]

Answer:

The driving time at 54 miles per hour is 37.04 hours.

Step-by-step explanation:

8 0
3 years ago
A furniture store received an order for 3,456 chairs. they can fit 9 chairs in a large shipping box. how many shipping boxes wil
kykrilka [37]
This is simple :)
If 9 chairs can fit in one box, and you have 3,456 chairs, just divide how many chairs you have by how many can fit in the box in order to find how many boxes you will need.

3,456/9 = 384
384 boxes will be needed
7 0
3 years ago
Hello, Can someone please explain on how to do this? thank you!
Marrrta [24]
Steps:

1) determine the domain

2) determine the extreme limits of the function

3) determine critical points (where the derivative is zero)

4) determine the intercepts with the axis

5) do a table

6) put the data on a system of coordinates

7) graph: join the points with the best smooth curve

Solution:

1) domain

The logarithmic function is defined for positive real numbers, then you need to state x - 3 > 0

=> x > 3 <-------- domain

2) extreme limits of the function

Limit log (x - 3) when x → ∞ = ∞

Limit log (x - 3) when x → 3+ = - ∞ => the line x = 3 is a vertical asymptote

3) critical points

dy / dx = 0 => 1 / x - 3 which is never true, so there are not critical points (not relative maxima or minima)

4) determine the intercepts with the axis

x-intercept: y = 0 => log (x - 3) = 0 => x - 3 = 1 => x = 4

y-intercept: The function never intercepts the y-axis because x cannot not be 0.

5) do a table

 x                          y = log (x - 3)

limit x → 3+            - ∞

3.000000001        log (3.000000001 -3) = -9

3.0001                  log (3.0001 - 3) = - 4

3.1                       log (3.1 - 3) = - 1

4                          log (4 - 3) = 0

13                       log (13 - 3) = 1

103                     log (103 - 3) = 10

lim x → ∞             ∞

Now, with all that information you can graph the function: put the data on the coordinate system and join the points with a smooth curve.
7 0
3 years ago
Read 2 more answers
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