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Vlad [161]
2 years ago
7

A psychologist is collecting data on the time it takes to learn a certain task. For 50 randomly selected adult subjects, the sam

ple mean is 16.40 minutes and the sample standard deviation is 4.00 minutes. Construct the 95 percent confidence interval for the mean time required by all adults to learn the task. Assume that X, the time to learn a task, is distributed normally.
Mathematics
1 answer:
tatuchka [14]2 years ago
8 0

Answer: (15.263,\ 17.537)

Step-by-step explanation:

According to the given information, we have

Sample size : n= 50

\overline{x}=16.40

s=4.00

Since population standard deviation is unknown, so we use t-test.

Critical value for  95 percent confidence interval  :

t_{n-1,\alpha/2}=t_{49, 0.025}= 2.009575\approx2.010

Confidence interval : \overline{x}\pm t_{n-1, \alpha/2}\dfrac{s}{\sqrt{n}}

16.40\pm (2.010)\dfrac{4}{\sqrt{50}}\\\\=16.40\pm1.13702770415\\\\=16.40\pm1.1370\\\\=(16.40-1.1370,\ 16.40+1.1370)\\\\=(15.263,\ 17.537)

Required 95% confidence interval :  (15.263,\ 17.537)

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The article "Expectation Analysis of the Probability of Failure for Water Supply Pipes"† proposed using the Poisson distribution
oksian1 [2.3K]

Answer:

a. P(X ≤ 5) = 0.999

b. P(X > λ+λ) = P(X > 2) = 0.080

Step-by-step explanation:

We model this randome variable with a Poisson distribution, with parameter λ=1.

We have to calculate, using this distribution, P(X ≤ 5).

The probability of k pipeline failures can be calculated with the following equation:

P(k)=\lambda^{k} \cdot e^{-\lambda}/k!=1^{k} \cdot e^{-1}/k!=e^{-1}/k!

Then, we can calculate P(X ≤ 5) as:

P(X\leq5)=P(0)+P(1)+P(2)+P(4)+P(5)\\\\\\P(0)=1^{0} \cdot e^{-1}/0!=1*0.3679/1=0.368\\\\P(1)=1^{1} \cdot e^{-1}/1!=1*0.3679/1=0.368\\\\P(2)=1^{2} \cdot e^{-1}/2!=1*0.3679/2=0.184\\\\P(3)=1^{3} \cdot e^{-1}/3!=1*0.3679/6=0.061\\\\P(4)=1^{4} \cdot e^{-1}/4!=1*0.3679/24=0.015\\\\P(5)=1^{5} \cdot e^{-1}/5!=1*0.3679/120=0.003\\\\\\P(X\leq5)=0.368+0.368+0.184+0.061+0.015+0.003=0.999

The standard deviation of the Poisson deistribution is equal to its parameter λ=1, so the probability that X exceeds its mean value by more than one standard deviation (X>1+1=2) can be calculated as:

P(X>2)=1-(P(0)+P(1)+P(2))\\\\\\P(0)=1^{0} \cdot e^{-1}/0!=1*0.3679/1=0.368\\\\P(1)=1^{1} \cdot e^{-1}/1!=1*0.3679/1=0.368\\\\P(2)=1^{2} \cdot e^{-1}/2!=1*0.3679/2=0.184\\\\\\P(X>2)=1-(0.368+0.368+0.184)=1-0.920=0.080

4 0
2 years ago
Given: AR ⊥ RS , TS ⊥ RS, AT=26, RS=24, AR=12 <br> Find: TS
BabaBlast [244]

Solution -

drawing a perpendicular from AQ to TS, we get a right angle triangle AQT

Using Pythagoras Theorem,

AT² = AQ² + QT²

⇒26² = 24² + QT²                    (∵ Due to symmetry AQ = RS)

⇒QT² = 676-576 = 100

⇒QT = 10

As TS = QT + QS = 12 + 10 = 22  ( ∵ Due to symmetry AR = QS )

∴ TS = 22 (ans)

3 0
2 years ago
Janet is drawing the path formed by the parametric equations x=2+3 sin t and y=1-1/2cos t. Which curve did she draw??
frosja888 [35]
Sin²t +cos²t =1

<span> x=2+3 sin t
sin t=(x-2)/3

</span><span>y=1-1/2cos t
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2 years ago
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Answer:

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Step-by-step explanation:

Using the 2 + (-20) + 8 to describe movement relative to sea level ;

2 can be taken as the starting point, positive values represents elevation above sea level ;

2 can be taken as 2 feet platform above sea level ;

- 20 represents distance dived from platform, negative signifies elevation below sea level ; the distance dived relative to sea level is (-20 + platform height)

(-20 + 2) = - 18

8 feets means a final elevation of 8 above sea level (positive value).

7 0
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artcher [175]
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8 0
2 years ago
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