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muminat
3 years ago
7

Provide an appropriate response. In order to efficiently bid on a contract, a contractor wants to be 95% confident that his erro

r is less than two hours in estimating 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?
a.19
b.4
c.5
d.20
Mathematics
1 answer:
lidiya [134]3 years ago
5 0

Answer:

d. 20

Step-by-step explanation:

Standard deviation is 4.5

Margin error for the problem is 2 hours

Probability 95%, that means that the siginficance level α is 1 – p

α = 1 – 0.95 = 0.05

margin of error (ME) can be defined as follows

ME = Z(α/2) * standard deviation/ √n

Where n is the sample size

Z(0.05/2) = Z(0.025)

Using a z table Z = 1.96

Now, replacing in the equation and find n

2 = 1.96 * 4.5/ √n

2 = 8.82/√n

√n = 8.82/2

√n = 4.41

n = 4.41^2

n = 19.44 ≈ 20

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Answer:

So we have two given angles- 31* and 43*.

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31* + 43* = 74*

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6 0
2 years ago
[6+4=10 points] Problem 2. Suppose that there are k people in a party with the following PMF: • k = 5 with probability 1 4 • k =
kirza4 [7]

Answer:

1). 0.903547

2). 0.275617

Step-by-step explanation:

It is given :

K people in a party with the following :

i). k = 5 with the probability of $\frac{1}{4}$

ii). k = 10 with the probability of $\frac{1}{4}$

iii). k = 10 with the probability $\frac{1}{2}$

So the probability of at least two person out of the 'n' born people in same month is  = 1 - P (none of the n born in the same month)

= 1 - P (choosing the n different months out of 365 days) = 1-\frac{_{n}^{12}\textrm{P}}{12^2}

1). Hence P(at least 2 born in the same month)=P(k=5 and at least 2 born in the same month)+P(k=10 and at least 2 born in the same month)+P(k=15 and at least 2 born in the same month)

= \frac{1}{4}\times (1-\frac{_{5}^{12}\textrm{P}}{12^5})+\frac{1}{4}\times (1-\frac{_{10}^{12}\textrm{P}}{12^{10}})+\frac{1}{2}\times (1-\frac{_{15}^{12}\textrm{P}}{12^{15}})

= 0.25 \times 0.618056 + 0.25 \times 0.996132 + 0.5 \times 1

= 0.903547

2).P( k = 10|at least 2 share their birthday in same month)

=P(k=10 and at least 2 born in the same month)/P(at least 2 share their birthday in same month)

= $0.25 \times \frac{0.996132}{0.903547}$

= 0.0.275617

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