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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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Which of the following expressions represents the distance between -13 and -4 on a number line
lesya692 [45]

Answer:

<h2>a) |-13 - (-4)|</h2>

Step-by-step explanation:

The formula of a distance between two points (numbers) A and B on the number line:

d = |B - A| = |A - B|

We have A = -13 and B = -4. Substitute:

d = |-13 - (-4)|

6 0
3 years ago
Eth enlarged the triangle below by a scale of 5.
levacccp [35]

Answer:

She should have multiplied one half (4)(3.5) by 5 squared.

Step-by-step explanation:

We are given that

Base of triangle=b=4 cm

Height of triangle=h=3.5 cm

Area of triangle=\frac{1}{2}bh=\frac{1}{2}(4)(3.5) cm^2

After enlarged

Scale factor=5

New base of enlarged triangle=b'=4(5) cm

Height of enlarged triangle=h'=3.5(5) cm

Area of enlarged triangle=\frac{1}{2}4(5)(3.5\times 5)=\frac{1}{2}(4)(3.5)(5^2) cm^2

But Beth wrote

Area of enlarged triangle=\frac{1}{2}(4)(3.5)(5)=35 cm^2

She should have multiplied one half (4)(3.5) by 5 squared.

3 0
3 years ago
How can you convert a fractions to a decimal if the fraction has a multiple of 10 in the denominator?
tester [92]
Divide the denominator by the numerator
6 0
3 years ago
Given parallelogram ABCD with c(5,4), find the coordinates of A if the diagonals intersect at (2,7)
vladimir1956 [14]

Answer: (-1, 10)

Step-by-step explanation:

7 0
2 years ago
An automobile with 0.279 m radius tires travels 65000 km before wearing them out. How many revolutions do the tires make, neglec
bija089 [108]

Answer:

Revolutions=37079108.61 rev

Step-by-step explanation:

First if all we have to make the units same to calculate the revolutions

Since distance gis gien in km and radius is given in m we will covert distance to m first.

Distance =S=65000km

Distance=S=65000km*1000m/km

Distance = S= 65000000m

Formula:

S=rθ

where

S is the distance

r is the radius

θ is the revolution in radian

θ=S/r

θ=65000000/0.279

θ=232974910.4 rad

Revolutions=θ/2π

Revolutions=232974910.4/2π

Revolutions=37079108.61 rev

7 0
3 years ago
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