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ASHA 777 [7]
2 years ago
13

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

ating 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? DON'T JUST GIVE THE ANSWER - SHOW WORK AND EXPLAIN YOUR PROCESS EACH STEP OF THE WAY SO THAT I CAN FOLLOW WHAT YOU DID AND CHECK YOUR WORK.
Mathematics
1 answer:
Sonja [21]2 years ago
8 0

Answer:

Step-by-step explanation:

Given that in order to efficiently bid on a contract, a contractor wants to be 95% confident that his error is less than two hours in estimating the average time it takes to install tile flooring.

Std deviation =4.5 errors

95% confidence interval = Mean±1.96*std dev

Hence we have

1.96(\frac{4.5}{\sqrt{n} } )

\sqrt{n} \geq 4.41\\n\geq 19.4481

Sample size should be 20.

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Answer:

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Step-by-step explanation:

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2 years ago
To avoid detection at customs, a traveler places 6 narcotic tablets in a bottle containing 9 vitamin tablets that are similar in
lukranit [14]

Answer: \dfrac{26}{27}

Step-by-step explanation:

Given : To avoid detection at customs, a traveler places 6 narcotic tablets in a bottle containing 9 vitamin tablets that are similar in appearance.

Proportion of success : p=\dfrac{6}{9}=\dfrac{2}{3}

Sample size taken by customs official : n= 3

Let x be a binomial variable that represents the tablets in the bottle.

Using Binomial probability formula :-

P(X=x)=^nC_xp^x(1-p)^{n-x}

The probability that the traveler will be arrested for illegal possession of narcotics =P(x\geq1)=1-P(x=0)

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Hence, the probability that the traveler will be arrested for illegal possession of narcotics = \dfrac{26}{27}

8 0
3 years ago
At the start of the week a bookshop had science and art books in the ratio 2:5. By the end of the week, 20% of each type of book
Anastaziya [24]
Let there be 2x science and 5x art books 
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<span>art books sold = 5x × 0.2 = x </span>
<span>art books unsold = 5x – x = 4x </span>

<span>total books unsold = 1.6x + 4x = 5.6x </span>
<span>5.6x = 2240 </span>
<span>x = 400 </span>

<span>2x science = 800 </span>
<span>and 5x art books = 2000 </span>
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3 years ago
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Maurinko [17]

Answer: um i don’t know what your asking me?

Step-by-step explanation:

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2 years ago
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liberstina [14]
7 plus 7 equals 14. Add one to that and you have 15 which is the answer.
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