In the Salk vaccine field trial, 400,000 children were part of a randomized controlled double-blind experiment. Just about half of them were assigned at random to the vaccine group, and the other half to the placebo.16 In the vaccine group, there were 57 cases of polio, compared to 142 in the placebo group. Is this difference due to chance? If not, what explains it?

Answer:

Step-by-step explanation:

From the given information:

The number of children that were randomly allocated to each vaccination group; n₁ = 200,000

No of polio cases X₁ = 57

Now, in the vaccine group:

the proportion of polio cases is:

[tex]\hat p_1 = \dfrac{57}{200000}[/tex]

=  0.000285

The number of children that were randomly allocated to the placebo group, n₂ = 200,000

No of polio cases X₂ = 142

In the placebo group

the proportion of polio cases is:

[tex]\hat p_2 = \dfrac{142}{200000}[/tex]

Null and alternative hypothesis is computed as follows:

H₀: There is no difference in the proportions of polio cases between both groups.  

H₁: There is a difference in the proportions of polio cases between both groups.

Let assume that the level of significance ∝ = 0.05

The test statistic  can be computed as:

[tex]Z = \dfrac{\hat p_1-\hat p_2}{\sqrt{\dfrac{\hat p_1 \hat q_1}{n_1}+ \dfrac{\hat p_2 \hat q_2}{n_2}}}[/tex]

[tex]Z = \dfrac{0.000285-0.000710}{\sqrt{\dfrac{0.000285(1-0.000285)}{200000}+ \dfrac{0.000710(1-0.000710)}{200000}}}[/tex]

[tex]Z = \dfrac{-4.25\times 10^{-4}}{\sqrt{\dfrac{0.000285(0.999715)}{200000}+ \dfrac{0.000710(0.99929)}{200000}}}[/tex]

Z = - 6.03

P-value =  2P(Z < -6.03)

From the Z - tables

P-value =  2 × 0.0000

= 0.000

We reject the H₀ provided that P-value is very less.

Therefore, we may conclude that there is a difference in the proportions of polio cases between the vaccine group and placebo group not due to chance.

Pls help my sister doesn't know this question ​

Identify the missing measures

Given the system of equations, what is the solution?

x + 2y = 7
x - 2y = -1

A.) {(-4, 6)}
B.) {(-8, -12}
C.) {(3,2)}

Which equation has the solution x = 2?
A. 5x + 1 = 10
B. 4x - x = 4
C. 3x + 2 = 8
D. 2x - 3 = 9

point a is located at 18 on the number line. point b is located at -14 on the number line.

what is the distance between point a and point b on the number line?

A statewide real estate sales agency, Farm Associates, specializes in selling farm property in the state of Nebraska. Its records indicate that the mean selling time of farm property is 90 days. Because of recent drought conditions, the agency believes that the mean selling time is now greater than 90 days. A statewide survey of 100 farms sold recently revealed that the mean selling time was 94 days, with a standard deviation of 22 days.

Required:
At the 0.10 significance level, has there been an increase in selling time?

100 Points!!!!! PLEASE HELP. Sarah’s neighbor offers to pay her $5 for every shark tooth she finds on the beach. After collecting only three shark’s teeth, Sarah decides to share the opportunity with her friend John. Sarah can find shark teeth twice as fast as John, but she can earn even more money with his help.

Sarah can use the expression 5(2j + 3 + j) to represent the amount of money they can earn.

Part 1: Writing Expressions

1. Write an expression that looks like Sarah’s expression: 5(2j + 3 + j). Replace the coefficients so that your expression is not equivalent. You may use any number that you choose to replace the coefficients. Be sure to leave the variables the same. For example, 8(3j + 7 + 3j) looks like Sarah’s expression but is not equivalent.

2. Translate the new algebraic expression you created in Question 1 to a verbal expression.

Part 2: Writing Equivalent Expressions

3. You will now use mathematical properties to create two expressions that are equivalent to the expression you created in Question 1. Make sure you show all steps in your work.

a. Use either the commutative property or combine like terms to create an equivalent expression.

b. Use the distributive property to create an equivalent expression.

4. Pick a number from 1 to 10. Use that number to verify your three expressions (the original, the one from 3a, and the one from 3b) are equivalent by substituting it into each expression. Show all your work for complete credit.

Part 3: Finish the Story

5. Write a few sentences to end Sarah’s story. How many shark teeth did she find? How many shark teeth did John find? How much money did they earn?

Step-by-step explanation:

Sarah’s neighbor offers to pay her $5 for every shark tooth she finds on the beach. After collecting only three shark’s teeth, Sarah decides to share the opportunity with her friend John. Sarah can find shark teeth twice as fast as John, but she can earn even more money with his help.

Sarah can use the expression 5(2j + 3 + j) to represent the amount of money they can earn.

Part 1: Writing Expressions

Q1. Write an expression that looks like Sarah’s expression: 5(2j + 3 + j). Replace the coefficients so that your expression is not equivalent. You may use any number that you choose to replace the coefficients. Be sure to leave the variables the same. For example, 8(3j + 7 + 3j) looks like Sarah’s expression but is not equivalent.

25(10j + 18 + 5j)

Your expression is good.

Q2. Translate the new algebraic expression you created in Question 1 to a verbal expression.

Skuttle offered to pay his sister Izzy $25 for every four-leaf clover she finds in the woods. Izzy finds 18 clovers but decides to get Roxy’s help. Izzy finds clovers twice as fast as Roxy but they will overall make more money together.

Your verbal expression is good. It reflects your chosen equation.

Use your knowledge of the mathematical properties to create two equivalent algebraic expressions for the algebraic expression you created in Question 1. Explain how you arrived at the equivalent expressions by showing all your steps and stating which properties you used.

Using commutative property of addition, the expression in question 1 can be rewritten as follows:



Using distributive property of multiplication over addition, the expression in question 1 can also be rewritten as follows:



Q 4. Use substitution to prove your algebraic expressions are equivalent. You may substitute any number for the variables you choose. Show all your work for complete credit.


Part 3: Finish the Story

Q5. Write a few sentences to end Sarah’s story. How many shark teeth did she find? How many shark teeth did John find? How much money did they earn?

lf 9/28 of the students at Williards High school participate in after school sports activities, what fraction of the students do not participate in after school activities

The pie chart shows the results of a survey on
students' favourite subjects.
a What fraction of the students chose Science?
b 60 students chose Maths.
i How many students chose Languages?
ii How many students chose Other?
jii How many students took part in the survey?
Favourite subjects
380 1200
O Mathis
Languages
Science
Art
DOther
90° 42
sh
o
a

if a=1 and b=2 what is the value of a²+b²?​

Please help me please

Sketch and Write the Equation

Equation=
Ordered Pair = (-3, 5)
Slope=
y-intercept= - 5

The angles shown below are supplementary:
What is the value of x?
BRAINLIEST
PLEASE HELP
SHOW WORK

Im on a girls basketball team , 3 are in sixth grade , 5 are in seventh grade , and 6 are in eighth grade . so which is the ratio of seventh graders to eighth graders on the team ?

What is the
average rate of change between:
x = 1 and x = 2?
x = 2 and x = 3?
X = 3 and x = 4?

Find the total surface area of a sphere radius being 7cm

-5 1/4 - (-7 1/2)

A) -12 3/4
B) 2 1/4
C) -2 1/4
D)2 3/4

The height , in feet, windowsills in a high-rise building is represented by this sequence: 3,15,27,39,...

Name that Circle Part!
Directions: Use the diagram to classify each circle part by clicking on, copy (ctrl+c) and pasting (ctrl+v) then dragging the appropriate part. Parts may be used more than once.

Find mT, rounded to the nearest degree.

What is the surface area of the
rectangular prism below?

A man made a loss of 4% on an article he had sold for Tzs 240 more he had made a profit of 8%. Find the cost price​

HELP WHAT COLOR DO I PICJ!!

The table includes the size of roofs (x) and the cost to replace them (y). The summary points are (748, 7,048), (890, 8,385), and (1,001, 8,475).
Using approximate values for the slope and y-intercept, what is the linear model?
y =
A. 0.8
B. 5.6
C. 9.4

x +
A. -299.2
B. 3,043.2
C. 7,265.4

Plz help me well mark brainliest if correct!!.....

Which of the following should not be used as justification in a formal proof?
Postulates
Theorems
Axioms
Venn diagrams

A bag contains 12 colored marbles. Dan drew a single marble from the bag 25 times, replacing the marble each time. He recorded drawing a red marble 9 times, a yellow marble 6 times, a blue marble 4 times, and a green marble 6 times. Based on these results, what is a reasonable conclusion about the makeup of the marbles in the bag?
Select one:

more red marbles than blue marbles

no white marbles

an equal number of yellow and blue marbles

more green marbles than red marbles

If you can help me with these 4 questions I'll give brainliest :))​

Shamus owes his parents $162. He pays them 60% of the $45 he earns as a soccer referee each week. How many weeks will it take Shamus to pay back all of the money he owes his parents?

.
PLEASE HELP ME

Which of the following is likely to have the
greatest variability?
A. The cost of a piece of candy from a vending
machine
B. The height of all the students at West Middle
School
The age of all the students in the sixth grade
D. The number of days in a month