# 11.13 Review

This module provides an review on Chi-Square Distribution as a part of Collaborative Statistics collection (col10522) by Barbara Illowsky and Susan Dean.

The next two questions refer to the following real study:

A recent survey of U.S. teenage pregnancy was answered by 720 girls, age 12 - 19. 6% of the girls surveyed said they have been pregnant. ( Parade Magazine ) We are interested in the true proportion of U.S. girls, age 12 - 19, who have been pregnant.

Find the 95% confidence interval for the true proportion of U.S. girls, age 12 - 19, who have been pregnant.

$\left(0\text{.}\text{0424},0\text{.}\text{0770}\right)$

The report also stated that the results of the survey are accurate to within ± 3.7% at the 95% confidence level. Suppose that a new study is to be done. It is desired to be accurate to within 2% of the 95% confidence level. What is the minimum number that should be surveyed?

2401

Given: $X$ ~ $\text{Exp}\left(\frac{1}{3}\right)$ . Sketch the graph that depicts: $P\left(x>1\right)$ .

The next four questions refer to the following information:

Suppose that the time that owners keep their cars (purchased new) is normally distributed with a mean of 7 years and a standard deviation of 2 years. We are interested in how long an individual keeps his car (purchased new). Our population is people who buy their cars new.

60% of individuals keep their cars at most how many years?

7.5

Suppose that we randomly survey one person. Find the probability that person keeps his/her car less than 2.5 years.

0.0122

If we are to pick individuals 10 at a time, find the distribution for the mean car length ownership.

$N\left(7,0\text{.}\text{63}\right)$

If we are to pick 10 individuals, find the probability that the sum of their ownership time is more than 55 years.

0.9911

For which distribution is the median not equal to the mean?

• Uniform
• Exponential
• Normal
• Student-t

B

Compare the standard normal distribution to the student-t distribution, centered at 0. Explain which of the following are true and which are false.

• As the number surveyed increases, the area to the left of -1 for the student-t distribution approaches the area for the standard normal distribution.
• As the degrees of freedom decrease, the graph of the student-t distribution looks more like the graph of the standard normal distribution.
• If the number surveyed is 15, the normal distribution should never be used.
• True
• False
• False

The next five questions refer to the following information:

We are interested in the checking account balance of a twenty-year-old college student. We randomly survey 16 twenty-year-old college students. We obtain a sample mean of $640 and a sample standard deviation of$150. Let $X$ = checking account balance of an individual twenty year old college student.

Explain why we cannot determine the distribution of $X$ .

If you were to create a confidence interval or perform a hypothesis test for the population mean checking account balance of 20-year old college students, what distribution would you use?

student-t with $\text{df}=\text{15}$

Find the 95% confidence interval for the true mean checking account balance of a twenty-year-old college student.

$\left(\text{560}\text{.}\text{07},\text{719}\text{.}\text{93}\right)$

Introduction about quantum dots in nanotechnology
what does nano mean?
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
it is a goid question and i want to know the answer as well
Maciej
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
for screen printed electrodes ?
SUYASH
What is lattice structure?
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
what's the easiest and fastest way to the synthesize AgNP?
China
Cied
types of nano material
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
what is nano technology
what is system testing?
1 It is estimated that 30% of all drivers have some kind of medical aid in South Africa. What is the probability that in a sample of 10 drivers: 3.1.1 Exactly 4 will have a medical aid. (8) 3.1.2 At least 2 will have a medical aid. (8) 3.1.3 More than 9 will have a medical aid.