Professor Elderman has given the same multiple-choice final exam in his Principles of Microeconomics class for many years. After
2 answers:
Answer:
And we can use the following z score:
And replacing we got using the normal standard distribution table or excel:
C.0.8413
Step-by-step explanation:
Previous concepts
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
The Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean".
Solution to the problem
Let X the random variable that represent the records of a population, and for this case we know the distribution for X is given by:
Where and
Since the distribution for X is normal then we know that the distribution for the sample mean is given by:
We select a sample of size n=36, and we want to calculate this probability:
And we can use the following z score:
And replacing we got using the normal standard distribution table or excel:
C.0.8413
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<h3>Answer: Choice B</h3>
The set notation includes all values from -5 to 0, but the domain only includes the integer values
eg: something like -1.2 is in the second set, but it is not in the set {-5,-4,-3,-2,-1}
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Further explanation:
Let's go through the answer choices one by one
- A. This is false because 0 does not come before -5, but instead -5 is listed first. The order -5,-4,-3,-2,-1,0 is correct meaning that
is the correct order as well.
- B. This is true. A value like x = -1.2 is in the set
since -1.2 is between -5 and 0; but -1.2 is not in the set {-5, -4, -3, -2, -1, 0}. So the distinction is that we're either considering integers only or all real numbers in this interval. To ensure that we only look at integers, the student would have to write
. The portion
means "x is in the set of integers". The Z refers to the German word Zahlen, which translates to "numbers".
- C. This is false. The student used the correct inequality signs to indicate x is -5 or larger and also 0 or smaller; basically x is between -5 and 0 inclusive of both endpoints. The "or equal to" portions indicate we are keeping the endpoints and not excluding them.
- D. This is false. Writing
would not make any sense. This is because that compound inequality breaks down into
. Try to think of a number that is both smaller than -5 AND also larger than 0. It can't be done. No such number exists.
Answer:
x = y²
Step-by-step explanation:
Any point (x, y ) on the parabola is equidistant from the focus and the directrix
Using the distance formula, then
= | x + 3 |
Squaring both sides
(x - 3)² + y² = (x + 3)² ← expanding both sides
x² - 6x + 9 + y² = x² + 6x + 9 ← subtract x² + 6x + 9 from both sides
- 12x + y² = 0 ( subtract y² from both sides )
- 12x = - y² ( divide both sides by - 12 )
x = y²