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Elden [556K]
3 years ago
11

There are 42 students in an elementary statistics class. On the basis of years of experience, the instructor knows that the time

needed to grade a randomly chosen first examination paper is a random variable with an expected value of 5 min and a standard deviation of 6 min. (Give answers accurate to 3 decimal places.)
(a) If grading times are independent and the instructor begins grading at 6:50 P.M. and grades continuously, what is the (approximate) probability that he is through grading before the 11:00 P.M. TV news begins?
1
(b) If the sports report begins at 11:10, what is the probability that he misses part of the report if he waits until grading is done before turning on the TV?
2

Mathematics
1 answer:
harkovskaia [24]3 years ago
5 0

Answer:

A) 0.99413

B) 0.00022

Step-by-step explanation:

A) First of all let's find the total grading time from 6:50 P.M to 11:00 P.M.:

Total grading time; X = 11:00 - 6:50 = 4hours 10minutes = 250 minutes

Now since we are given an expected value of 5 minutes, the mean grading time for the whole population would be:

μ = n*μ_s ample = 42 × 5 = 210 minutes

While the standard deviation for the population would be:

σ = √nσ_sample = √(42 × 6) = 15.8745 minutes

To find the z-score, we will use the formula;

z = (x - μ)/σ

Thus;

z = (250 - 210)/15.8745

z = 2.52

From the z-distribution table attached, we have;

P(Z < 2.52) ≈ 0.99413

B) solving this is almost the same as in A above, the only difference is an additional 10 minutes to the time.

Thus, total time is now 250 + 10 = 260 minutes

Similar to the z-formula in A above, we have;

z = (260 - 210)/15.8745

z = 3.15

P(Z > 3.15) = 0.00022

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Read 2 more answers
Please check these please
antoniya [11.8K]

-5x=60

The first thing we want to do is to divide -5 on both sides. We do this because -5x, is the same as -5 times x and we want to do the inverse of that.

After we divide on both sides, we get    x=60/-5

We know that 60 divided by -5 is -12.

Therefore our answer is:      x=-12

----------------------------------------------------------------------------------------------------------

5= n + 2

We always want to get the variable to be alone, so if we subtract by 5 we would be doing the opposite of getting the variable alone. Although, if we subtract by 2 on both sides, we would get the variable alone and the answer would be 3=n

Therefore our answer is:       False

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2(x-7)

By looking at this question, we see x being subtracted by 7. Then we see that 2 is being multiplied to that.

Therefore our answer is:        C

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The product of a number and 4 increased by 8

In these types of questions, it's smart to break it up. We will start with the product of a number and 4. We know that a number is a variable and if we look at the multiple choice answers we can see that the variable they chose to use is n. We also know that a product is when numbers get multiplied. So that means 4 and n get multiplied which turns into 4n.

For the other part of the problem, we know that increased by 8 means added my 8. Now that we got our answers, we put then together.


Therefore our answer is:       A    4n+8

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Pls give a like if this helped you!!!

4 0
2 years ago
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Answer:

wouldn't that be...24x²?

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