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ser-zykov [4K]
3 years ago
13

The time until failure of an electronic device has an exponential distribution with mean 15 months. If a random sample of five s

uch devices are tested, what is the probability that the first failure among the five devices occurs a after 9 months? b before 12 months?
Mathematics
1 answer:
Ainat [17]3 years ago
6 0

Answer:

The probability that the first failure occurs among the five devices is given by

(a) 9 months =\frac{9}{15} or  =0.6

(b) 12 months=\frac{12}{15} or = 0.8

Step-by-step explanation:

probability is given as the; number of required outcome/ total number of possible outcome.

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Answer:

o solve an quadratic equation using factoring : 1 . Transform the equation using standard form in which one side is zero. ... Set each factor to zero (Remember: a product of factors is zero if and only if one or more of the factors is zero).

Step-by-step explanation:

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Order these rational numbers in order from least to greatest 1/5 and -0.4 and -1/4 and 0.5
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-0.4, -1/4, 1/5, 0.5
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The width of rectangle A is the sum of twice a number and 8. The length of the rectangle is 3 times as great as the width. If th
Galina-37 [17]
Formula for perimeter of a rectangle = 2(L + W)
let the number be x
width = 2x + 8
length = 3(2x + 8)
substitute respectively
96 = 2 (2x + 8 + 3(2x + 8)) open the bracket
96 = 2 ( 2x + 8 + 6x + 24) collect like terms
96 = 2 (8x + 32) open the bracket
96 = 16x + 64
collect like terms
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2 = x
therefore, the width = 2x + 8 = 2(2) + 8 = 4 + 8 = 12.
and the length = 3(2x + 8) = 6x + 24 = 6(2) + 24 = 12 + 24 = 36.
4 0
3 years ago
Several years​ ago, 38​% of parents who had children in grades​ K-12 were satisfied with the quality of education the students r
Colt1911 [192]

Answer:

0.428 - 1.96\sqrt{\frac{0.428(1-0.428)}{1165}}=0.3995

0.428 + 1.96\sqrt{\frac{0.428(1-0.428)}{1165}}=0.4564

We are confident that the true proportion of people satisfied with the quality of education the students receive is between (0.3995, 0.4564), since the lower value for this confidence level is higher than 0.38 we have enough evidence to conclude that the parents' attitudes toward the quality of education have changed.

Step-by-step explanation:

For this case we are interesting in the parameter of the true proportion of people satisfied with the quality of education the students receive

The confidence level is given 95%, the significance level would be given by \alpha=1-0.95=0.05 and \alpha/2 =0.025. And the critical values are:

z_{\alpha/2}=-1.96, z_{1-\alpha/2}=1.96

The estimated proportion of people satisfied with the quality of education the students receive is given by:

\hat p =\frac{499}{1165}= 0.428

The confidence interval for the proportion if interest is given by the following formula:  

\hat p \pm z_{\alpha/2}\sqrt{\frac{\hat p (1-\hat p)}{n}}

And replacing the info given we got:

0.428 - 1.96\sqrt{\frac{0.428(1-0.428)}{1165}}=0.3995

0.428 + 1.96\sqrt{\frac{0.428(1-0.428)}{1165}}=0.4564

We are confident that the true proportion of people satisfied with the quality of education the students receive is between (0.3995, 0.4564), since the lower value for this confidence level is higher than 0.38 we have enough evidence to conclude that the parents' attitudes toward the quality of education have changed.

8 0
4 years ago
How do you write 72% as a fraction in simplest form?
Step2247 [10]
72% = 72/100

72/100=36/50=18/25 
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3 years ago
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