Given that mean=3750 hours and standard deviation is 300:
Then:
<span>a. The probability that a lamp will last for more than 4,000 hours?
P(x>4000)=1-P(x<4000)
but
P(x<4000)=P(z<Z)
where:
z=(x-</span>μ)/σ
z=(4000-3750)/300
z=0.833333
thus
P(x<4000)=P(z<0.8333)=0.7967
thus
P(x>4000)=1-0.7967=0.2033
<span>b.What is the probability that a lamp will last less than 3,000 hours?
P(x<3000)=P(z<Z)
Z=(3000-3750)/300
z=-2.5
thus
P(x<3000)=P(z<-2.5)=0.0062
c. </span><span>.What lifetime should the manufacturer advertise for these lamps in order that only 4% of the lamps will burn out before the advertised lifetime?
the life time will be found as follows:
let the value be x
the value of z corresponding to 0.04 is z=-2.65
thus
using the formula for z-score:
-2.65=(x-3750)/300
solving for x we get:
-750=x-3750
x=-750+3750
x=3000</span>
Answer:
cohort study
Step-by-step explanation:
Given that an investigator reviewed the medical records of 200 children seen for care at Boston Medical Center in the past year who were between the ages 8 and 12 and identified 40 children with asthma. He also identified 40 children of the same ages who were free of asthma. Each child and their family were interviewed to assess whether there might be an association between certain environmental factors such as exposure to second-hand smoke.
The objective of this experiment is to test the causes of the disease asthma and to find the risk factors and environment causing this disease.
So this cannot come under randomized control nor case control.
Cross over study is to put to two different environments two groups and study. But here nothing is influenced actual environments are studied
Hence this comes under cohort study
Answer:
3x+4y-12=0
y intercept = -constant term/coefficient. of y
= 12/4
=3
You do Y2-Y1 Divided by X2-X1
Answer:
the answer is C (280 square feet)
Step-by-step explanation:
First, cut the lawn so that it becomes two shapes: a rectangle, and a triangle. Solve for both areas.
A(r) = lw
A(r) = (14)(16)
A(r) = 224 square feet
A(t) = bh/2
A(t) = (8)(14) / 2
A(t) = 112 / 2
A(t) = 56 square feet
Add the two areas:
A(r) + A(t) = Area of lawn
224 square feet + 56 square feet = 280 square feet.
