Answer:
The correct answer is - C. 24.1%
Step-by-step explanation:
Given:
mean μ = 65%
standard deviation δ = 7.1 %
solution:
Prob( X>70) = 1 - Prob(x<70)
= P (x-μ/δ ≥ 70 -65/7.1)
= 1 - Prob( (70-65)/7.1)
= 1 - Prob ( z < 0.7042553)
= 0.24065
the percentage of students scoring 70 or more in the exam
= 24.065*100
= 24.1%
the center is at the origin of a coordinate system and the foci are on the y-axis, then the foci are symmetric about the origin.
The hyperbola focus F1 is 46 feet above the vertex of the parabola and the hyperbola focus F2 is 6 ft above the parabola's vertex. Then the distance F1F2 is 46-6=40 ft.
In terms of hyperbola, F1F2=2c, c=20.
The vertex of the hyperba is 2 ft below focus F1, then in terms of hyperbola c-a=2 and a=c-2=18 ft.
Use formula c^2=a^2+b^2c
2
=a
2
+b
2
to find b:
\begin{gathered} (20)^2=(18)^2+b^2,\\ b^2=400-324=76 \end{gathered}
(20)
2
=(18)
2
+b
2
,
b
2
=400−324=76
.
The branches of hyperbola go in y-direction, so the equation of hyperbola is
\dfrac{y^2}{b^2}- \dfrac{x^2}{a^2}=1
b
2
y
2
−
a
2
x
2
=1 .
Substitute a and b:
\dfrac{y^2}{76}- \dfrac{x^2}{324}=1
76
y
2
−
324
x
2
=1 .
Answer:
Is an experimental study
Step-by-step explanation:
In an observational study you don't control any aspect of the investigation you just observe the variables that you determined since the beginning without any intervention.
In this case you are controlling who sees one or the other video, then you are controlling one of the variables that is the type of video each group sees and because of this it is an experimental study. Researchers designed an experiment to prove the null hypothesis they had.
