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e-lub [12.9K]
3 years ago
11

A store has 80 modems in its inventory, 30 coming from Source A and the remainder from Source B. Of the modems from Source A, 20

% are defective. Of the modems from Source B, 8% are defective. Calculate the probability that exactly two out of a sample of five modems selected without replacement from the store’s inventory are defective.
Mathematics
1 answer:
RUDIKE [14]3 years ago
7 0

Answer:

0.102

Step-by-step explanation:

The number of defective modems in the inventory is 20% * 30 + 8% * 0.50 =10 (out of 80)

Note that the number of defectives in the inventory is fixed i.e. we are told that there is 1/8 probability that a modem in the inventory is defective, but rather that exactly 1/8 of all modems are defective.

The probability that exactly two modems in a random sample of five are defective is :

(10↓2)(70↓3) / (80↓5) = 0.102

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A machine that produces ball bearings has initially been set so that the true average diameter of the bearings it produces is .5
lara [203]

Answer:

7.3% of the bearings produced will not be acceptable

Step-by-step explanation:

Problems of normally distributed samples can be 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.

In this problem, we have that:

\mu = 0.499, \sigma = 0.002

Target value of .500 in. A bearing is acceptable if its diameter is within .004 in. of this target value.

So bearing larger than 0.504 in or smaller than 0.496 in are not acceptable.

Larger than 0.504

1 subtracted by the pvalue of Z when X = 0.504.

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

Z = \frac{0.504 - 0.494}{0.002}

Z = 2.5

Z = 2.5 has a pvalue of 0.9938

1 - 0.9938= 0.0062

Smaller than 0.496

pvalue of Z when X = -1.5

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

Z = \frac{0.496 - 0.494}{0.002}

Z = -1.5

Z = -1.5 has a pvalue of 0.0668

0.0668 + 0.0062 = 0.073

7.3% of the bearings produced will not be acceptable

4 0
3 years ago
Few students manage to complete their schooling without taking a standardized admissions test such as the Scholastic Achievement
slega [8]

Answer:

Step-by-step explanation:

Assuming there is a punitive removal of one point for an incorrect response.

Five undiscernable choices: 20% chance of guessing correctly -- Expectation: 0.20*(1) + 0.80*(-1) = -0.60

Four undiscernable choices: 25% chance of guessing correctly -- Expectation: 0.25*(1) + 0.75*(-1) = -0.50

I'll use 0.33 as an approzimation for 1/3

Three undiscernable choices: 33% chance of guessing correctly -- Expectation: 0.33*(1) + 0.67*(-1) = -0.33 <== The approximation is a little ugly.

Two undiscernable choices: 50% chance of guessing correctly -- Expectation: 0.50*(1) + 0.50*(-1) = 0.00

And thus we see that only if you can remove three is guessing neutral. There is no time when guessing is advantageous.

One Correct Answer: 100% chance of guessing correctly -- Expectation: 1.00*(1) + 0.00*(-1) = 1.00

6 0
3 years ago
To estimate μ, the mean salary of full professors at American colleges and universities, you obtain the salaries of a random sam
GenaCL600 [577]

Answer:

<h3>73220±566.72</h3>

Step-by-step explanation:

The formula for calculating the confidence interval is expressed as;

CI = xbar ± z*s/√n

xbar is the sample mean =  $73,220

z is the z score at 99% CI = 2.576

s is the standard deviation = $4400

n is the sample size = 400

Substitute the given values into the formula;

CI = 73,220 ± 2.576*4400/√400

CI = 73,220 ± 2.576*4400/20

CI = 73,220± (2.576*220)

CI = 73220±566.72

Hence a 99% confidence interval for μ is 73220±566.72

5 0
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You walk 2/15 miles for your chemistry class to Your economics class at a constant speed of 0.8 miles per hour.How long did this
Zolol [24]
<span>speed = 2.5 miles per hour</span>
7 0
3 years ago
Decompose 3/8 as the sum of unit fractions
bearhunter [10]
Unit fractions are fractions with a 1 as the numerator(number on top)
so 3/8 equals 1/8+1/8+1/8
8 0
3 years ago
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