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3 years ago

On a test, a student got 80% of the items correct. If the student got 56 items correct, how many items were on the test?

1 answer:

7 0

80% of what is 56
0.80x = 56
x = 56/0.80
x = 70

check..
80% of 70 is 56
.80(70) = 56
56 = 56 (correct)

so there were 70 items on the test

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g A programmer plans to develop a new software system. In planning for the operating system that he will use, he needs to estim

kipiarov [429]

Answer:

a) n= 1045 computers

b) n= 442 computers

c) A. Yes, using the additional survey information from part (b) dramatically reduces the sample size.

Step-by-step explanation:

Hello!

The variable of interest is

X: Number of computers that use the new operating system.

You need to find the best sample size to take so that the proportion of computers that use the new operating system can be estimated with a 99% CI and a margin of error no greater than 4%.

The confidence interval for the population proportion is:

p' ± $Z_{1-\alpha /2}$ * $\sqrt{\frac{p'(1-p')}{n} }$

$Z_{1-\alpha /2}= Z_{0.995}= 2.586$

a) In this item there is no known value for the sample proportion (p') when something like this happens, you have to assume the "worst-case scenario" that is, that the proportion of success and failure of the trial are the same, i.e. p'=q'=0.5

The margin of error of the interval is:

d= $Z_{1-\alpha /2}$ * $\sqrt{\frac{p'(1-p')}{n} }$

$\frac{d}{Z_{1-\alpha /2}} = \sqrt{\frac{p'(1-p)}{n} }$

$(\frac{d}{Z_{1-\alpha /2}})^2 = \frac{p'(1-p')}{n}$

$n * (\frac{d}{Z_{1-\alpha /2}})^2 = p'(1-p')$

$n= [p'(1-p')]*(\frac{Z_{1-\alpha /2}}{d} )^2$

$n=[0.5(1-0.5)]*(\frac{2.586}{0.04} )^2= 1044.9056$

n= 1045 computers

b) This time there is a known value for the sample proportion: p'= 0.88, using the same confidence level and required margin of error:

$n= [p'(1-p')]*(\frac{Z_{1-\alpha /2}}{d} )^2$

$n= [0.88*0.12]*(\frac{{2.586}}{0.04})^2= 441.3681$

n= 442 computers

c) The additional information in part b affected the required sample size, it was drastically decreased in comparison with the sample size calculated in a).

I hope it helps!

4 0

4 years ago

Hey please help posted picture of question

Verdich [7]

By definition we have:
In mathematics, an irrational number is a number that can not be expressed as a fraction m / n, where m and n are integers and n is different from zero.
It is any real number that is not rational, and its decimal expression is neither exact or periodic.
Answer:
B. False

5 0

3 years ago

Read 2 more answers

32 thousand 1 hundred 4 ones times 10

vazorg [7]

Answer:

32140

Step-by-step explanation:

3 0

3 years ago

Round the number to the place of the underlined digit

PtichkaEL [24]

Answer:

Step-by-step explanation:

29,484

4, Does not round

the second 4, rounds to 5 because of the 8,

then The 9 would round and be 30

if its a decimal then it would be 30.0

if not then i think it would be 30,500 or 29,500 if we were to stop at the 9 and not round it

5 0

3 years ago

What is the solution of the system? Use substitution

Andreyy89

<span>B. (-3, 13)

I hope this helps. (:
</span>

7 0

3 years ago