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3 years ago

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A recent study showed that teenagers who had night light in their rooms as babies are more likely to suffer from myopia than tee

nagers who had not used night lights. But genetic factors are known to play a role, and near-sighted parents are more likely to install a night light in their children's room.This makes it hard to tell if the night light caused the subsequent myopia. This is an example of
A. double-blinding
B. the placebo effect
C.confounding
D.control
E. an explanatory variable

1 answer:

Reil [10]3 years ago

8 0

Answer:

I think its B. Im like 87% sure its B

Step-by-step explanation:

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Mopeds (small motorcycles with an engine capacity below 50 cm3) are very popular in Europe because of their mobility, ease of op

Anika [276]

Answer:

The probability that the maximum speed is at most 49 km/h is 0.8340.

Step-by-step explanation:

Let the random variable<em> </em><em>X</em> be defined as the maximum speed of a moped.

The random variable <em>X</em> is Normally distributed with mean, <em>μ</em> = 46.8 km/h and standard deviation, <em>σ</em> = 1.75 km/h.

To compute the probability of a Normally distributed random variable we first need to convert the raw score of the random variable to a standardized or <em>z</em>-score.

The formula to convert <em>X</em> into <em>z</em>-score is:

$z=\frac{X-\mu}{\sigma}$

Compute the probability that the maximum speed is at most 49 km/h as follows:

Apply continuity correction:

P (X ≤ 49) = P (X < 49 - 0.50)

= P (X < 48.50)

$=P(\frac{X-\mu}{\sigma}$

*Use a <em>z</em>-table for the probability.

Thus, the probability that the maximum speed is at most 49 km/h is 0.8340.

8 0

4 years ago

A solid rectangular box with height 5 m and square base with side lengths 4 m is built using a lightweight material whose densit

elena55 [62]

Answer:

627200LJ

Step-by-step explanation:

Height of box=5 m

Side of square base=4 m

Volume of rectangular box= $l\times b\times h$

Using the formula

Volume of rectangular box= $4\times 4\times 5=80m^3$

Density of material= $800kg/m^3$

We know that

$Mass=Density\times volume$

Using the formula

Mass of rectangular box= $80\times 800=64000 kg$

Gravity= $g=9.8m/s^2$

Weight of rectangular box,F= $mg=64000\times 9.8 N$

Let L be the vertical distance traveled by box

Total work done = $W=F\times displacement$

Therefore,total work done against gravity = $64000\times 9.8 L$ =627200 L J

Hence, the box requires work against gravity=627200LJ

5 0

3 years ago

Write an equation of the line in slope-intercept form

Agata [3.3K]

Answer:

y=2x-2

Step-by-step explanation:

Slope intercept form = y=mx+b

Where m=slope and b= y intercept

Reminder: the y intercept is where x=0

Looking at the graph, the y intercept is given as (0,-2)

There are also two points given (0, -2) and (2,2)

Reminder: to find the slope, divide the changes in y by the changes in x or substitute the numbers into this equation: y2-y1/x2-x1

2-(-2)/2-0=4/2

m=2

Now that we have the slope and y intercept, sbstitute into the equation y=mx+b:

y=2x-2

5 0

3 years ago

Read 2 more answers

Classify the numbers as prime or composite. numbers:37, 65, 71, 82

blondinia [14]

37:prime 65:composite 71:composite 82:composite

3 0

3 years ago

Read 2 more answers

Is the answer a, b, c, or d.

ale4655 [162]

The correct answer is d.

We have the following system of linear equations:

(I) $4x+7y=-14$
(II) $8x+5y=8$

Let's use the elimination method, then let's multiply the equation (1) $\times(-2)$ and subtracting (I) and (II):

(I) $-2(4x+7y)=-2(-14)$
∴ $-8x-14y=28$

(I) $-8x-14y=28$
(II) $8x+5y=8$
____________________
(III) $-9y=36$

∴ $y=-4$

We can find the value of x by substituting y either in (I) or (II). Thus, from (I):

$4x+7(-4)=-14$
∴ $4x-28=-14$
∴ $4x=14$
∴ $x=\frac{14}{4}$
∴ $\boxed{x=\frac{7}{2}}$

Let's substitute the values of x and y into (I) and (2)

(I) $4(\frac{7}{2})+7(-4)=14-28=-14$
(II) $8(\frac{7}{2})+5(-4)=28-20=8$

Finally the answer is:

$\boxed{x=\frac{7}{2} \rightarrow x= 3 \frac{1}{2}}$

4 0

3 years ago