Here is a simple probability model for multiple-choice tests. Suppose that each student has probability p of correctly answering a question chosen at random from a universe of possible questions. (A strong student has a higher p than a weak student.) The correctness of an answer to a question is independent of the correctness of answers to other questions. Jodi is a good student for whom p = 0.81.
Required:
a. Use the Normal approximation to find the probability that Jodi scores 77% or lower on a 100-question test.
b. If the test contains 250 questions, what is the probability that Jodi will score 77% or lower?
c. How many questions must the test contain in order to reduce the standard deviation of Jodi's proportion of correct answers to half its value for a 100-item test?
d. Laura is a weaker student for whom p = 0.76. Does the answer you gave in (c) for standard deviation of Jodi's score apply to Laura's standard deviation also?
Answer:
a) 0.8461 = 84.61% probability that Jodi scores 77% or lower on a 100-question test.
b) 0.9463 = 94.63% probability that Jodi will score 77% or lower.
c) 400 questions.
d) Yes, because the formula is the same, independently of the value of p.
Step-by-step explanation:
To solve this question, we need to understand the normal probability distribution and the central limit theorem.
Normal Probability Distribution:
Problems of normal distributions can be solved using the z-score formula.
In a set with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex], the z-score of a measure X is given by:
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
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 p-value, we get the probability that the value of the measure is greater than X.
Central Limit Theorem
The Central Limit Theorem estabilishes that, for a normally distributed random variable X, with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex], the sampling distribution of the sample means with size n can be approximated to a normal distribution with mean [tex]\mu[/tex] and standard deviation [tex]s = \frac{\sigma}{\sqrt{n}}[/tex].
For a skewed variable, the Central Limit Theorem can also be applied, as long as n is at least 30.
For a proportion p in a sample of size n, the sampling distribution of the sample proportion will be approximately normal with mean [tex]\mu = p[/tex] and standard deviation [tex]s = \sqrt{\frac{p(1-p)}{n}}[/tex]
In this question:
[tex]p = 0.81[/tex]
Question a:
100 questions means that [tex]n = 100[/tex]
For the approximation, we have that:
[tex]\mu = p = 0.81[/tex]
[tex]s = \sqrt{\frac{p(1-p)}{n}} = \sqrt{\frac{0.81*0.19}{100}} = 0.0392[/tex]
This probability is the pvalue of Z when X = 0.77. So
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
By the Central Limit Theorem
[tex]Z = \frac{X - \mu}{s}[/tex]
[tex]Z = \frac{0.77 - 0.81}{0.0392}[/tex]
[tex]Z = 1.02[/tex]
[tex]Z = 1.02[/tex] has a pvalue of 0.8461
0.8461 = 84.61% probability that Jodi scores 77% or lower on a 100-question test.
Question b:
Now [tex]n = 250[/tex], so:
[tex]s = \sqrt{\frac{p(1-p)}{n}} = \sqrt{\frac{0.81*0.19}{250}} = 0.0248[/tex]
[tex]Z = \frac{X - \mu}{s}[/tex]
[tex]Z = \frac{0.77 - 0.81}{0.0248}[/tex]
[tex]Z = 1.61[/tex]
[tex]Z = 1.61[/tex] has a pvalue of 0.9463
0.9463 = 94.63% probability that Jodi will score 77% or lower.
Question c:
The formula for the standard deviation is:
[tex]s = \sqrt{\frac{p(1-p)}{n}}[/tex]
Meaning that it is inversely proportional to the square root of the sample size.
So, to reduce the standard deviation by half, the number of question must be multiplied by (2)^2 = 4.
100*4 = 400
So 400 questions.
d. Laura is a weaker student for whom p = 0.76. Does the answer you gave in (c) for standard deviation of Jodi's score apply to Laura's standard deviation also?
Yes, because the formula is the same, independently of the value of p.
if an inheritance was shared among 72000 to the beneficiaries there were 3 children Ban , Michel and Bob in the ratio of 1:3:4 .how much will each get
Answer:
Ban has 9,000
Michel has 27,000
Bob has 36,000
Step-by-step explanation:
BA: MI: BO
1: 3: 4 (1+3+4 = total number)
BA: [tex]\frac{1}{8}[/tex] of 72,000 (72,000 ÷ 8 x 1) = 9,000
MI: [tex]\frac{3}{8}[/tex] of 72,000 (72,000 ÷ 8 x 3) = 27,000
BO: [tex]\frac{4}{8}[/tex] of 72,000 (72,000 ÷ 8 x 4) = 36,000
Is b+b+b x c x c x c is a equivalent expressions?
A. True
B. False
Look at the table below.
x y
3 1.8
5 3
7 4.2
9 5.4
11 6.6
Which of the following represents the constant of proportionality for the relationship shown in the table above?
A. 1.2
B. 0.7
C. 2
D. 0.6
An airplane is flying 4 miles directly over your house. The distance between your house and the airport is 12 miles. How far apart are the airplane and the airport?
Answer:
c=7.180 miles. 2. Jack is on one side of a 200-foot-wide canyon and Jill is on the other. Jack and Jill can both ... a=2.947 miles. 5. Airplane A is flying directly toward the airport which is 20 miles away. The pilot notices ...
What is the area of △STU rounded to the nearest tenth?
Answer:
38.7 units²
Step-by-step explanation:
4.6/SV = SV/8.1
SV² = 37.26
SV = 6.1
area = 1/2(8.1)(6.1) + 1/2(4.6)(6.1) = 38.7 units²
Choose the expression that best represents the phrase below.
... the product of the width and the height...
A. Wh
B. w-h
C. W + h
D. h w
E. W:h
F. h-w
Answer:
option E is your correct answer
mark as brainliest
what is 81 divided by 9
Answer:
9
Step-by-step explanation:
9
9x9 = 81
Therefore, 81 ÷ 9 is 9
AABC maps the outline of a new park. What is the area of the park?
Answer:
C. 10
Step-by-step explanation:
AC = 4 units
BC = 5 units
use the triangle formula
1/2 × 4 × 5 = 10
Erik has 5 blue marbles and 13 red marbles in a box. He randomly draws one out. Find P(Red) in fraction form.
Answer:
13/5
Step-by-step explanation:
The probability of (red) is the chance of drawing a red marble out of the red and blue marbles. As there are 13 red marbles and 5 blue marbles, the probability of drawing a red marble is 13 out of 5, or 13/5 in fraction form.
a group of students collected old newspapers for a recycling project. the data shows the mass, in kilograms, of old newspapers collected by each student.
23, 35, 87, 64, 101, 90, 45, 76, 105, 60, 55
98, 122, 49, 15, 57, 75, 120, 56, 88, 45, 100.
A.) Find the range of the mass of the newspapers collected.
B.) Find the interquartile range.
Answer:
A. 107 kg
B. 49 kg
Step-by-step explanation:
Exercise 5.16.1: Coin flips and events. About A coin is flipped four times. For each of the events described below, express the event as a set in roster notation. Each outcome is written as a string of length 4 from {H, T}, such as HHTH. Assuming the coin is a fair coin, give the probability of each event. (a) The first and last flips come up heads. Solution (b) There are at least two consecutive flips that come up heads.
Answer:
[tex](a)\ Pr = 0.25[/tex]
[tex](b)\ Pr = 0.50[/tex]
Step-by-step explanation:
Given
[tex]Flips = 4[/tex]
First, we calculate the sample size;
The coin has two possible outcomes (i.e. head or tail) and the number of flips is 4.
So, the sample size (N) is:
[tex]N = 2^4[/tex]
[tex]N = 16[/tex]
Solving (a): Probability the outcome of the first and last flip is head.
The possible outcomes for this event are:
[tex]n = \{(HHHH), (HHTH), (HTHH),(HTTH)\}[/tex]
[tex]n(n) = 4[/tex]
The probability is:
[tex]Pr = \frac{n(n)}{N}[/tex]
[tex]Pr = \frac{4}{16}[/tex]
[tex]Pr = 0.25[/tex]
Solving (a): Probability that the outcome of at least 2 consecutive flips is head.
The possible outcomes for this event are:
[tex]n = \{(HHHH), (HHHT),(HHTH), (HTHH),(THHH),(TTHH),(HHTT), (THHT)\}[/tex]
[tex]n(n) = 8[/tex]
The probability is:
[tex]Pr = \frac{n(n)}{N}[/tex]
[tex]Pr = \frac{8}{16}[/tex]
[tex]Pr = 0.50[/tex]
There are two ways to go from Fujairah to Sharjah , and four ways to go from Sharjah to Dubai. How many different ways are there to go from Fujairah to Dubai, passing through Sharjah?
6
8
16
12
Answer:
8
Step-by-step explanation:
Peter had 6 crayons. Mike gave Peter some more crayons. Then Peter had
13 crayons in all. How many crayons did Mike give Peter?
What type of problem is this, add to/take from: put together/take apart,
or compare? Type your response here.
Solve the problem in the space below.
Answer:
7
Step-by-step explanation:
13-6=7 compare maybe.....
You earn $86,000 the first year you graduate from college with a master's degree in chemical engineering. If you should be saving 25% of your gross pay, how much should you save?
A. $21,500
B. $64,500
C. $18,300
D. $12,400
Solve 3x2 + 4x + 2 = 0 by using the Quadratic Formula. If necessary, round to the nearest hundredth.
Answer:
Step-by-step explanation:
For this equation: a=3, b=4, c=2
3x2+4x+2=0
Step 1: Use quadratic formula with a=3, b=4, c=2.
x= −b±√b2−4ac / 2a
x= −(4)±√(4)2−4(3)(2) / 2(3)
x= −4±√−8 / 6
Answer:
No real solutions.
The quadratic equation 3x² + 4x + 2 = 0 does not have a real solution.
What are Quadratic Equations?Quadratic equations are second degree polynomial equations which is of the form ax² + bx + c = 0, where a, b and c are integers.
Given quadratic equation is,
3x² + 4x + 2 = 0
Quadratic formula to find the solution is,
x = [-b ± [tex]\sqrt{b^2-4ac}[/tex]] / 2a, where [tex]\sqrt{b^2-4ac}[/tex] is called discriminant.
Here, a = 3, b = 4 and c = 2
Substituting,
x = [-4 ± [tex]\sqrt{4^2-(4*3*2)}[/tex]] / (2 × 3)
= [-4 ± √(16 - 24)] / 6
= [-4 ± √(-8)] / 6
This has no real solution since the value inside the discriminant is negative.
Hence the quadratic equation has no real solution.
Learn more about quadratic Equations here :
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Brainliest for correct answer
Answer:
A. 549.5
Step-by-step explanation:
Evaluate the expression for x = 2 and y = 4 . (x ^ 5 * y ^ 7) / (x ^ 3 * y ^ 5) numbers only
Answer:
Answer is 64.
Step-by-step explanation:
524288/8192 = 64
A 3-column table with 4 rows titled 90-Day Forecast. Column 1 is labeled Weather Type with entries wind, rain, clouds, sunshine. Column 2 is labeled Predicted frequency with entries 9, 18, 27, 36. Column 3 is labeled Observed frequency with entries 12, 15, 33, 30.
The table shows the results of the experiment to determine the 90-day weather forecast. How does the experimental probability compare to the theoretical probability?
The theoretical probability for rain is 1/5. The experimental probability for rain is
.
The actual weather is
the theoretical probability.
1/6
approximately the same as
Answer:
✔1/6
✔ approximately the same as
Step-by-step explanation:
Here's proof
The length of a park bench is 1.5 meters. What is the length of the bench in millimeters?
Answer:
1500 millimeters
Step-by-step explanation:
1 meter = 1000 millimeters
1.5 meters = 1500 millimeters
A pet store worker weighs each kitten to the
nearest 0.05 kilogram. This dot plot shows the
weights.
Weights of Kittens
1.2
1.3
1.4
Weight (kilograms)
3 How much more does the heaviest kitten
weigh than the lightest kitten?
A 0.3 kg
C 0.25 kg
B 0.5 kg
D 2.4 kg
(a) select all the describe bd
Answer:
First - Perpendicular Bisector
Second - Angle Bisector
Fourth - Altitude
Step-by-step explanation:
It is not the median because it does not touch the base in the middle.
Solve for the unknown values.
Answer:
y=45° x=81°
Step-by-step explanation:
the 2 angles across the outside angles sum up to the given number so just subtract 95-50= 45, with that we know subtract from the total sum of every triangle which is 180. So we add the 2 angles we have now, 50+45=99. Now we subtract, 180-99= 81.
(4-i)(2+5i) simplify
Answer: 13+18i
Step-by-step explanation:
(4-i)(2+5i)
8+20i-2i-5(i)^2
as we know that i^2=-1
8+18i-5(-1)
8+18i+5
13+18i
Using traditional methods it takes 101 hours to receive an advanced driving license. A new training technique using Computer Aided Instruction (CAI) has been proposed. A researcher believes the new technique may reduce training time and decides to perform a hypothesis test. After performing the test on 280 students, the researcher decides to reject the null hypothesis at a 0.05 level of significance.
What is the conclusion?
a. There is sufficient evidence at the 0.02level of significance that the new technique reduces training time.
b. There is not sufficient evidence at the 0.02 level of significance that the new technique reduces training time.
Use the diagram to complete the statements.
The measure of minor arc EF i
The measure of angle DAB is
35.5
.5
71
109
Answer:
EF is 109
DAB is 54.5
Step-by-step explanation:
Applying the central angle theorem, the correct statement would be:
Measure of minor arc EF = 109°Measure of angle DAB = 54.5°What is the Central Angle Theorems?The central angle theorem states that:
Measure of intercepted arc = 1/2(measure of inscribed angle)Measure of central angle = measure of intercepted arcThus:
Measure of minor arc EF = m∠ECF = 109°
m∠DAB = 1/2(109°) [m∠ECF = m∠BAD = 109°]
m∠DAB = 54.5°
Therefore, applying the central angle theorem, the correct statement would be:
Measure of minor arc EF = 109°Measure of angle DAB = 54.5°Learn more about central angle theorem on:
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Solve each proportion 3/39= y/13
Answer:
[tex]y = 1[/tex]
Step-by-step explanation:
[tex] \frac{3}{39} = \frac{y}{13} [/tex]
Cross multiply
[tex]39 = 39y[/tex]
Divide by 39
[tex]y = 1[/tex]
Answer:
[tex]\boxed {\boxed {\sf y=1}}[/tex]
Step-by-step explanation:
To solve the proportion, we must solve for the variable. This is done by isolating the variable.
[tex]\frac {3}{39}= \frac {y}{13}[/tex]
The variable, y, is being divided by 13. The inverse of division is multiplication. Multiply both sides of the proportion by 13.
[tex]13*\frac {3}{39}= \frac {y}{13}*13[/tex]
[tex]13*\frac {3}{39}=y\\1=y[/tex]
Another way to solve is by cross multiplying. Multiply the 1st numerator by the 2nd denominator, then the 1st denominator and the 2nd numerator.
[tex]\frac {3}{39}= \frac {y}{13}[/tex]
[tex]3*13=39*y\\39=39y[/tex]
Divide both sides by 39 to isolate the variable.
[tex]39/39=39y/39 \\1=y[/tex]
In this proportion, y is equal to 1.
Robert bought some plants for his garden. Each plant costs $3.75.
If he spent a total of $52.50, how many plants did he buy?
Show your thinking.
نيانا
The inequality
Find all missing angles in the diagram