what is a case control study

Answers

Answer 1

Answer:

A study that compares two groups of people: those with the disease or condition under study (cases) and a very similar group of people who do not have the disease or condition (controls). Researchers study the medical and lifestyle histories of the people in each group to learn what factors may be associated with the disease or condition. For example, one group may have been exposed to a particular substance that the other was not. Also called retrospective study.

Step-by-step explanation:

Answer 2

Answer:

A case-control study is designed to help determine if an exposure is associated with an outcome (i.e., disease or condition of interest).

Step-by-step explanation:


Related Questions

at the present time, gerald is eight less than five times his nephews age. seven years ago gerald was 9 times his nephews age.
(A)if g represents geralds age now and n represents his nephews age today. use a system of equations that could be used to model this scenario?
(B)than use the equations to determine algebraically the ages of both Gerald and his nephew.
(C)than determine in how many years Gerald will be three times as old as his nephew?

Answers

Hiiiiiiiiiiiiiiiiiiiiiiiiiiiii

What you know about rollin' down in the deep?

When your brain goes numb, you can call that mental freeze

When these people talk too much, put that sh*t in slow motion, yeah

I feel like an astronaut in the ocean, ayy

What you know about rollin' down in the deep?

When your brain goes numb, you can call that mental freeze

When these people talk too much, put that sh*t in slow motion, yeah

I feel like an astronaut in the ocean

The Rockwell hardness of a metal is determined by impressing a hardened point into the surface of the metal and then measuring the depth of penetration of the point. Suppose the Rockwell hardness of a particular alloy is normally distributed with mean 70 and standard deviation 3. (Rockwell hardness is measured on a continuous scale.)a. If a specimen is acceptable only if its hardness is between 67 and 75, what is the probability that a randomly chosen specimen has an acceptable hardness?b. If the acceptable range of hardness is (70-c, 70+c) , for what value of c would 95% of all specimens have acceptable hardness?c. If the acceptable range is as in part (a) and the hardness of each of ten randomly selected specimens is independently determined, what is the expected number of acceptable specimens among the ten?d. What is the probability that at most eight of ten independently selected specimens have a hardness of less than73.84? [Hint: Y = the number among the ten specimens with hardness less than 73.84 is a binomial variable; what is p?]

Answers

Answer:

a) The probability that a randomly chosen specimen has an acceptable hardness is 0.7938.

b) If the acceptable range of hardness is (70-c, 70+c), then the value of c would 95% of all specimens have an acceptable hardness of 5.88.

c) Expected number of acceptable specimens among the ten is 7.938.

d) Binomial with n = 10 and p = P(X < 73.84)

[tex]p = P(Z <(73.84 - 70) / 3 ) = P(Z < 1.28) = 0.8997\\\\P(X <= 8) = 1 - P(X = 9) - P(X = 10)\\= 0.2650635[/tex]

Step-by-step explanation:

a )

[tex]P(67 < X< 75) = P( (67 - 70) / 3 < X < (75 - 70) / 3 )\\\\= P( - 1 < Z < 1.67) = 0.9525 - 0.1587 = 0.7938[/tex]

b )

[tex]c = 1.96 * 3 = 5.88[/tex]                    { Since Z = 1.96 for 95% CI refer table.}

c )

Expected number of acceptable specimens among the ten [tex]= 10 * P(67 < X< 75) \\\\= 10 * 0.7938 = 7.938[/tex]

d )

Binomial with n = 10 and p = P(X < 73.84)

[tex]p = P(Z <(73.84 - 70) / 3 ) = P(Z < 1.28) = 0.8997\\\\P(X <= 8) = 1 - P(X = 9) - P(X = 10)\\= 0.2650635[/tex]

Assume that a population is normally distributed with a mean of 100 and a standard deviation of 15. Would it be unusual for the mean of a sample of 3 to be 115 or more? Why or why not?

Answers

Answer:

|Z| < 2, which means that it would not be unusual for the mean of a sample of 3 to be 115 or more.

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.

If [tex]|Z| > 2[/tex], the value of X is considered to be unusual.

Central Limit Theorem

The Central Limit Theorem establishes 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.

Assume that a population is normally distributed with a mean of 100 and a standard deviation of 15.

This means that [tex]\mu = 100, \sigma = 15[/tex]

Sample of 3

This means that [tex]n = 3, s = \frac{15}{\sqrt{3}}[/tex]

Would it be unusual for the mean of a sample of 3 to be 115 or more? Why or why not?

We have to find the z-score.

[tex]Z = \frac{X - \mu}{\sigma}[/tex]

By the Central Limit Theorem

[tex]Z = \frac{X - \mu}{s}[/tex]

[tex]Z = \frac{115 - 100}{\frac{15}{\sqrt{3}}}[/tex]

[tex]Z = 1.73[/tex]

|Z| < 2, which means that it would not be unusual for the mean of a sample of 3 to be 115 or more.

Can I have help I am stuck on this problem It would mean the world if u helped me and tysm!! =-)

Answers

Answer:

Step-by-step explanation:

Wage = rate / hr * the number of hours worked.

Wage = ?

rate = 15.45

time = 29.25 hours

Wage = 15.45 * 29.25

Wage = 451.91

help pls
Draw a line segment AB=8cm. Construct angle BAC=angle ABC=60 DEGREE.
Now draw the angular bisector of each angle of angle ABC.
pls help

Answers

Answer:

Step-by-step explanation:

Bisection implies dividing a given segment into equal haves by construction. So that in the given question, angle ABC would be divided into equal parts.

After drawing segment AB to given length, use a compass to construct the required angle ABC. Then use the ends of the arc for the angle to bisect the angle.

The construction to this question is herewith attached to this answer for more clarifications.

When we expand (2x + 1/2)^6, what is the coefficient on the x^4 term?

Answers

Answer: The coefficient before x^4 is 60

Step-by-step explanation:

Hey! So I am not an expert at this, but you have to use the binomial theorem

I have attached of the Pascals Triangle (one shows the row numbering as well)

Basically in a pascal triangle, you add the two numbers above it to get the next number below

As you can see, the rows start from 0 instead of 1

The 6th row contains the numbers 1, 6, 15, 20, 15, 6, 1 which would be the coefficient terms

NOTE: the exponents always add to 6, the first term starts at 6 and decrease it's exponent by 1 each time (6, 5, 4, 3, 2, 1, 0) and the second term increases it's exponent by 1 each time (0, 1, 2, 3, 4, 5, 6)

Using this information the third term from the sixth row (15) would be where it is x^4 (I have circled it on the second image)

It would be 15 × 2^4 × (1/2)^2 = 60

The reason why it is 2^4 and (1/2)^2 is because the third term has the exponents 4 and 2 (bolded on the NOTE) which means that the first term must be put to the power of 4 and the second term must be put to the 2nd power

Sorry for the lousy explanation. I really hope this makes sense! Let me know if this helped :)

Which of the following expressions have a difference of 5? Check all that apply.
VX
0-3-(-8)
-2-3
1-(-4)
07-(-2)

Answers

9514 1404 393

Answer:

  A, C

Step-by-step explanation:

A: -3 -(-8) = -3 +8 = 5

B: -2 -3 = -5

C: 1 -(-4) = 1 +4 = 5

D: 7 -(-2) = 7 +2 = 9

__

Differences A and C are 5.

Answer: A: -3- (-8)

B:1 -(-4)

Step-by-step explanation:

in A your subtracting them in B your adding them

Find the difference of (4.2x10^3)-(2.7x10^3)
Show work!

Answers

Step-by-step explanation:

Is it helpful ?

plz let me know

Find the Diameter of the circle, whose radius is 17 cm.

Answers

Answer:

34 cm

Step-by-step explanation:

The radius is half of the diameter, so 17 cm is half of 34 cm.

Diameter = 34 cm

A pizza company runs a marketing campaign based on their delivery time for pizzas. They claim that they will deliver a pizza within 30 minutes of ordering or it is free. In practice the time it takes to prepare a pizza and it being delivered is normally distributed with mean 25 minutes and standard deviation 3 minutes. What is the probability a pizza is delivered for free?On a particular Sunday, 40 pizzas were ordered. What is the probability that more than 2 were delivered for free?If the company wants to reduce the proportion of pizzas that are delivered free to 1%, what should the delivery time be advertised as?

Answers

Answer:

0.0475 = 4.75% probability a pizza is delivered for free.

0.2955 = 29.55% probability that more than 2 were delivered for free.

The delivery time should be advertised as 32 minutes.

Step-by-step explanation:

To solve this question, we need to understand the binomial distribution and the normal distribution.

Binomial probability distribution

The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.

[tex]P(X = x) = C_{n,x}.p^{x}.(1-p)^{n-x}[/tex]

In which [tex]C_{n,x}[/tex] is the number of different combinations of x objects from a set of n elements, given by the following formula.

[tex]C_{n,x} = \frac{n!}{x!(n-x)!}[/tex]

And p is the probability of X happening.

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.

Normally distributed with mean 25 minutes and standard deviation 3 minutes.

This means that [tex]\mu = 25, \sigma = 3[/tex]

What is the probability a pizza is delivered for free?

More than 30 minutes, which is 1 subtracted by the p-value of Z when X = 30.

[tex]Z = \frac{X - \mu}{\sigma}[/tex]

[tex]Z = \frac{30 - 25}{3}[/tex]

[tex]Z = 1.67[/tex]

[tex]Z = 1.67[/tex] has a p-value of 0.9525

1 - 0.9525 = 0.0475

0.0475 = 4.75% probability a pizza is delivered for free

What is the probability that more than 2 were delivered for free?

Multiple pizzas, so the binomial probability distribution is used.

0.0475 probability a pizza is delivered for free, which means that [tex]p = 0.0475[/tex]

40 pizzas, which means that [tex]n = 40[/tex]

This probability is:

[tex]P(X > 2) = 1 - P(X \leq 2)[/tex]

In which

[tex]P(X \leq 2) = P(X = 0) + P(X = 1) + P(X = 2)[/tex]

So

[tex]P(X = x) = C_{n,x}.p^{x}.(1-p)^{n-x}[/tex]

[tex]P(X = 0) = C_{40,0}.(0.0475)^{0}.(0.9525)^{40} = 0.1428[/tex]

[tex]P(X = 1) = C_{40,1}.(0.0475)^{1}.(0.9525)^{39} = 0.2848[/tex]

[tex]P(X = 2) = C_{40,2}.(0.0475)^{2}.(0.9525)^{38} = 0.2769[/tex]

Then

[tex]P(X \leq 2) = P(X = 0) + P(X = 1) + P(X = 2) = 0.1428 + 0.2848 + 0.2769 = 0.7045[/tex]

[tex]P(X > 2) = 1 - P(X \leq 2) = 1 - 0.7045 = 0.2955[/tex]

0.2955 = 29.55% probability that more than 2 were delivered for free.

If the company wants to reduce the proportion of pizzas that are delivered free to 1%, what should the delivery time be advertised as?

The 99th percentile, which is X when Z has a p-value of 0.99, so X when Z = 2.327.

[tex]Z = \frac{X - \mu}{\sigma}[/tex]

[tex]2.327 = \frac{X - 25}{3}[/tex]

[tex]X - 25 = 2.327*3[/tex]

[tex]X = 32[/tex]

The delivery time should be advertised as 32 minutes.

A bag contains 6 black, 4 blue, and 8 white marbles. What is the probability that a marble drawn from the bag will be white?
a.1/18
b.2/5
c.4/9
d.4/5

Answers

Answer:

C.4/9

Step-by-step explanation:

You add the black marbles, blue marbles, and the white marbles together, which equal 18. Out of the 18 marbles, 8 of them are white so it would be 8/18.

but you have to simplify it. 8 and 18 have 2 as the greatest common factor. 8 divided by 2 is 4 and 18 divided by 2 is 9. Finally its 4/9 since you cant simplify it even more.

is the sum of two rational numbers sometimes zero ture or false?​

Answers

Answer:

True.

Step-by-step explana

-4/5 + 4/5 is 0

construct a scale of A-sharp major on a treble staff in ascending order only​

Answers

Answer: In the picture from the basic music theory website's page on a-sharp  major scale

Step-by-step explanation: music theory

course
Look at the following number line:
- 10
-5
0
5
10
What are two ways to write the inequality graphed?
x>-1 and -1 XS-1 and -12X
x < -1 and -1 > X
x2-1 and -1 5x

Answers

first and last one i think

Please help! What is the domain of the function shown in the graph?

Answers

Answer:

nnmb cgchmfxmgfmv vb  ,  mnio qrstuvwxyz

abcdefghijklmnoprstuvxxyz

Step-by-step explanation:

now i know my abcs next time wont you sing with me

Ms.James shared 5/8 of the candies she had in a bag and had 15 left.How many candies did she have before sharing?​

Answers

Answer:

40

Step-by-step explanation:

If you take 15, and divide it by the 3 out of the 3/8 left, you get 5. You then multiply 5 by 8 to get the full amount of candies she had before sharing, 40.

I hope this helped!

Thanks!

Your friend in answering,

~Steve

Answer:

40.

Step-by-step explanation:

If 15 candies are the rest of 3/8, then the total candies were 40.

I need help I’ll give u brainlest

Answers

Answer:

[tex]150[/tex] cubic centimeters

Step-by-step explanation:

Volume for triangular prism is  [tex]V=\frac{1}{2} bhl[/tex]

[tex]V=\frac{1}{2}(6)(5)(10)[/tex]

[tex]V=\frac{1}{2} (300)[/tex]

[tex]V=150[/tex]

Hope this helps

Answer:

150 cubic centimeters

Step-by-step explanation:

The formula for the volume of a Triangular prism:

A=1/2*b*h*l

plug everything in

1/2*6*5*10=150 Cubic centimeters

Factor this polynomial.
.-2x2 - 7x-3

Answers

Answer:

Its B

Step-by-step explanation:

Mark as Brainllest!!

What is the slope of the line represented by the equation f(x) = -3x + 7?

A -7
B -3
C 3
D 7

Answers

Answer:

-3

Step-by-step explanation:

in these equations the slope is multiplied by x which is -3 in this one.

Answer:

[tex]-3[/tex]

Step-by-step explanation:

The equation of a line is [tex]y=mx+b[/tex], and m is the gradient which is the slope. Hence, the number with x is the slope, which is [tex]-3[/tex].

Hope that helped.

If you apply these changes to the linear parent function, f(x) = x, what is the
equation of the new function?
• Vertically compress by a factor of 7.
• Shift up 9 units.
O A. DY) = 7x+9
O B. g(x) = = x+9
O C. () = 7(x-9)
O D. g(x) = + (x+9)

Answers

Answer:

The equation of the new function is [tex]g(x) = 7x + 9[/tex]

Step-by-step explanation:

Vertically compress by a factor of 7.

Vertically compressing a function by a units is the same as:

[tex]g(x) = f(ax)[/tex]

In this question:

[tex]f(x) = x, a = 7[/tex]. So

[tex]g(x) = f(7x) = 7x[/tex]

Shift up 9 units.

Shifting a function up a units is the same thing as adding a to the function. In this case, [tex]a = 9[/tex], and then:

[tex]g(x) = 7x + 9[/tex]

The equation of the new function is [tex]g(x) = 7x + 9[/tex]

Which is the graph of f(x) = 2 (4)?
5
40.4)
404)
4
(4,4)
3
3
3 2
2
2
2
(2.1)
6,2)
1
5 -4 -3 -2 -14
1
3
4
-5 4 -3 -2 -14
234
-5 6 -3 -2 -14
2
3
4
5
X
-2
-2
نا دیا
-3
-3
4
W4
-5
5
Tu
5
4
(
24)

Answers

Answer:

The Third one

Step-by-step explanation:

Your Welcome :)

Graph of the function is attached below.

Correct option is D.

What is exponential function?

As the name suggests, the exponential function contains an exponent. Note, however, that the exponential function has a constant as its base and a variable as its exponent, not vice versa (if a function has a variable as its base and a constant as its exponent, it is a power function). The exponential function can be in one of the following forms:

Definition of exponential function

In mathematics, an exponential function is a function of the form f(x) = aˣ. where "x" is a variable and "a" is a constant  called the base of the function, which must be greater than 0.

Given, exponential function

f(x) = (1/4)4ˣ

exponential function is defined for x∈R

Putting x = 0

f(0) = (1/4)4⁰

f(0) = 1/4

Point on curve is (0,1/4)

Putting x = 1

f(1) = (1/4)4¹

f(1) = (1/4)4

f(1) = 1

Point on curve is (1,1)

Putting x = 2

f(2) = (1/4)4²

f(2) = (1/4)16

f(2) = 4

Point on curve is (2,4)

Putting x = 3

f(3) = (1/4)4³

f(3) = (1/4)64

f(3) = 16

Point on curve is (3,16)

Point (0, 1/4), (1, 1), (2, 4), (3, 16) can be used to draw graph of the function.

Hence, graph of the function is drawn as follows.

Learn more about exponential function here:

https://brainly.com/question/14355665

#SPJ7

Evaluate: 11c+5a-8 for a=4 and c=-6

Answers

Answer:

- 54

Step-by-step explanation:

11 c + 5 a - 8

11 × -6 + 5 × 4 - 8 (given :- a = 4 and b = -6)

- 66 + 20 - 8

- 54

by how much is 2690 less than 3780​

Answers

Step-by-step explanation:

Subtract 2690 from 3780

3780

-2690

=1090

which of the following statements is true

Answers

Answer: B ACE is similar to DCB

Step-by-step explanation:

what is the square root of 15

Answers

Step-by-step explanation:

[tex] \sqrt{15} = 3.872983346 = 3.88[/tex]

giving brainliest to whomever answers correctly!​

Answers

Answer:

B: A systematic random sample

Step-by-step explanation:

Systematic sampling is a type of probability sampling in which members of a larger population are chosen at random from a larger population but at a fixed, periodic interval. This interval, also known as the sampling interval, is calculated by dividing the population size by the sample size desired. Despite the fact that the sample population is chosen in advance, systematic sampling is still considered random if the periodic interval is set in advance and the starting point is chosen at random.

Hope this helps and if it does, don't be afraid to give my answer a "Thanks" and maybe a Brainliest if it's correct?  

Which answer describes the pattern in this sequence?

2, 1, 12, 14, ...


multiply by 2

subtract 1

add 12

multiply by 12

Answers

I think the answer is to Multiply by 12

Chet has $1200 invested in a bank account modeled by the function P(n) = 1200(1.002)

Answers

Answer:

Answer: 3) R(n) = 1200(1.002)n - 100n

Step-by-step explanation:

After n months, which function represents Chet’s net worth, R(n)?

(1) R(n) = 1200(1.002)n + 100n

(2) R(n) = 1200(1.002)12n + 100n

(3) R(n) = 1200(1.002)n - 100n

(4) R(n) = 1200(1.002)12n - 100n

Answer: 3) R(n) = 1200(1.002)n - 100n

Net worth is the amount of his savings minus his debt,

Everything in the problem is in terms of months, so there is no need to multiply the exponent by 12, which would convert n years into months.

Another name for NQ is? (Geometry)

Answers

Answer:

NQ : Summary

CodeNQOne-letter codeXMolecule name2-HYDROXYNAPHTHOQUINONESynonyms2-HYDROXY-1,4-NAPHTHOQUINONESystematic namesProgram Version Name ACDLabs 10.04 2-hydroxynaphthalene-1,4-dione OpenEye OEToolkits 1.5.0 2-hydroxynaphthalene-1,4-dione

A team of researchers wants to determine whether pet owners are generally more satisfied with their lives than non-pet owners. To test their theory, the researchers randomly select 500 pet owners and 500 non-pet owners from several major metropolitan areas in the country. The researchers then interview the individuals, asking them a series of questions. Each response is assessed with a point value that is later translated to a satisfaction indicator. Of the pet owners surveyed, 380 of the 500 were found to be satisfied with their lives, while 336 of the 500 non-pet owners were found to be satisfied.
Would this study be considered an experiment or an observational study?

Answers

Answer:

observational study

Step-by-step explanation:

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