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kotykmax [81]
3 years ago
10

A study of the amount of time it takes a mechanic to rebuild the transmission for a 1992 Chevrolet Cavalier shows that the mean

is 8.4 hours and the standard deviation is 1.8 hours. If 40 mechanics are randomly selected, find the probability that their mean rebuild time exceeds 9.1 hours.
A ) 0.1046 B) 0.0069 C ) 0.1285 D ) 0.0046
Mathematics
1 answer:
Dovator [93]3 years ago
6 0

Answer:

B) 0.0069

Step-by-step explanation:

To solve this question, we need to understand the normal probability distribution and the central limit theorem.

Normal probability distribution

Problems of normally distributed samples are solved using the z-score formula.

In a set with mean \mu and standard deviation \sigma, the zscore of a measure X is given by:

Z = \frac{X - \mu}{\sigma}

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.

Central Limit Theorem

The Central Limit Theorem estabilishes that, for a normally distributed random variable X, with mean \mu and standard deviation \sigma, the sampling distribution of the sample means with size n can be approximated to a normal distribution with mean \mu and standard deviation s = \frac{\sigma}{\sqrt{n}}.

For a skewed variable, the Central Limit Theorem can also be applied, as long as n is at least 30.

In this question, we have that:

\mu = 8.4, \sigma = 1.8, n = 40, s = \frac{1.8}{\sqrt{40}} = 0.2846

Find the probability that their mean rebuild time exceeds 9.1 hours.

This is 1 subtracted by the pvalue of Z when X = 9.1. So

Z = \frac{X - \mu}{\sigma}

By the Central Limit Theorem

Z = \frac{9.1 - 8.4}{0.2846}

Z = 2.46

Z = 2.46 has a pvalue of 0.9931

1 - 0.9931 = 0.0069

So the answer is B.

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3 years ago
If m^2 = 3 then what is the value of 5m^6<br><br> a. 15<br> b. 30<br> c. 45<br> d. 135
Virty [35]

Answer:

135

Step-by-step explanation:

m^2 = 3

Cube m^2

(m^2)^3 = 3^3

m^(2*3) = 27

m^6 = 27

Now multiply by 5

5 * m^6 = 5*27

5 m^6 =135

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4) BRAINLIEST + 15 + POINTS :)
malfutka [58]

Answer:

C

Step-by-step explanation:

New equation: y = -3(2y + 3) - 4

Distribute and simplify: y = -6y - 13

Add 6y: 7y = -13

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3 years ago
The graph of f(x) = x2 has been shifted into the form f(x) = (x − h)2 + k: a parabola with a vertex of 4, negative 2 What is the
katrin [286]

Answer:

k = -2

Step-by-step explanation:

f(x) = (x − h)² + k

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3 years ago
A survey of 1,562 randomly selected adults showed that 522 of them have heard of a new electronic reader. The accompanying techn
tester [92]

Answer:

a) We want to test the claim that 35​% of adults have heard of the new electronic reader, then the system of hypothesis are.:  

Null hypothesis:p=0.35  

Alternative hypothesis:p \neq 0.35  

And is a two tailed test

b) z=\frac{0.334 -0.35}{\sqrt{\frac{0.35(1-0.35)}{1562}}}=-1.326  

c) p_v =2*P(z  

d) Null hypothesis:p=0.35  

e) Fail to reject the null hypothesis because the P-value is greater than the significance level, alpha.

Step-by-step explanation:

Information provided

n=1562 represent the random sample selected

X=522 represent the people who have heard of a new electronic reader

\hat p=\frac{522}{1562}=0.334 estimated proportion of people who have heard of a new electronic reader

p_o=0.35 is the value to verify

\alpha=0.05 represent the significance level

z would represent the statistic

p_v represent the p value

Part a

We want to test the claim that 35​% of adults have heard of the new electronic reader, then the system of hypothesis are.:  

Null hypothesis:p=0.35  

Alternative hypothesis:p \neq 0.35  

And is a two tailed test

Part b

The statistic for this case is given :

z=\frac{\hat p -p_o}{\sqrt{\frac{p_o (1-p_o)}{n}}} (1)  

Replacing the info given we got:

z=\frac{0.334 -0.35}{\sqrt{\frac{0.35(1-0.35)}{1562}}}=-1.326  

Part c

We can calculate the p value using the laternative hypothesis with the following probability:

p_v =2*P(z  

Part d

The null hypothesis for this case would be:

Null hypothesis:p=0.35  

Part e

The best conclusion for this case would be:

Fail to reject the null hypothesis because the P-value is greater than the significance level, alpha.

5 0
3 years ago
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