# 2.14 Univariate descriptive statistics: homework

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Descriptive Statistics: Homework is part of the collection col10555 written by Barbara Illowsky and Susan Dean and provides homework questions related to lessons about descriptive statistics.

Twenty-five randomly selected students were asked the number of movies they watched the previous week. The results are as follows:

# of movies Frequency Relative Frequency Cumulative Relative Frequency
0 5
1 9
2 6
3 4
4 1

• Find the sample mean $\overline{x}$
• Find the sample standard deviation, $s$
• Construct a histogram of the data.
• Complete the columns of the chart.
• Find the first quartile.
• Find the median.
• Find the third quartile.
• Construct a box plot of the data.
• What percent of the students saw fewer than three movies?
• Find the 40th percentile.
• Find the 90th percentile.
• Construct a line graph of the data.
• Construct a stem plot of the data.
• 1.48
• 1.12
• 1
• 1
• 2
• 80%
• 1
• 3

The median age for U.S. blacks currently is 30.9 years; for U.S. whites it is 42.3 years. (( Source: http://www.usatoday.com/news/nation/story/2012-05-17/minority-births-census/55029100/1) )

• Based upon this information, give two reasons why the black median age could be lower than the white median age.
• Does the lower median age for blacks necessarily mean that blacks die younger than whites? Why or why not?
• How might it be possible for blacks and whites to die at approximately the same age, but for the median age for whites to be higher?

Forty randomly selected students were asked the number of pairs of sneakers they owned. Let X = the number of pairs of sneakers owned. The results are as follows:

X Frequency Relative Frequency Cumulative Relative Frequency
1 2
2 5
3 8
4 12
5 12
7 1
• Find the sample mean $\overline{x}$
• Find the sample standard deviation, $s$
• Construct a histogram of the data.
• Complete the columns of the chart.
• Find the first quartile.
• Find the median.
• Find the third quartile.
• Construct a box plot of the data.
• What percent of the students owned at least five pairs?
• Find the 40th percentile.
• Find the 90th percentile.
• Construct a line graph of the data
• Construct a stem plot of the data
• 3.78
• 1.29
• 3
• 4
• 5
• 32.5%
• 4
• 5

600 adult Americans were asked by telephone poll, What do you think constitutes a middle-class income?The results are below. Also, include left endpoint, but not the right endpoint. ( Source: Time magazine; survey by Yankelovich Partners, Inc. )

"Not sure" answers were omitted from the results.
Salary ($) Relative Frequency <20,000 0.02 20,000 - 25,000 0.09 25,000 - 30,000 0.19 30,000 - 40,000 0.26 40,000 - 50,000 0.18 50,000 - 75,000 0.17 75,000 - 99,999 0.02 100,000+ 0.01 • What percent of the survey answered "not sure"? • What percent think that middle-class is from$25,000 - \$50,000 ?
• Construct a histogram of the data
1. Should all bars have the same width, based on the data? Why or why not?
2. How should the<20,000 and the100,000+ intervals be handled? Why?
• Find the 40th and 80th percentiles
• Construct a bar graph of the data

Following are the published weights (in pounds) of all of the team members of the San Francisco 49ers from a previous year ( Source: San Jose Mercury News )

• 177
• 205
• 210
• 210
• 232
• 205
• 185
• 185
• 178
• 210
• 206
• 212
• 184
• 174
• 185
• 242
• 188
• 212
• 215
• 247
• 241
• 223
• 220
• 260
• 245
• 259
• 278
• 270
• 280
• 295
• 275
• 285
• 290
• 272
• 273
• 280
• 285
• 286
• 200
• 215
• 185
• 230
• 250
• 241
• 190
• 260
• 250
• 302
• 265
• 290
• 276
• 228
• 265

• Organize the data from smallest to largest value.
• Find the median.
• Find the first quartile.
• Find the third quartile.
• Construct a box plot of the data.
• The middle 50% of the weights are from _______ to _______.
• If our population were all professional football players, would the above data be a sample of weights or the population of weights? Why?
• If our population were the San Francisco 49ers, would the above data be a sample of weights or the population of weights? Why?
• Assume the population was the San Francisco 49ers. Find:
• the population mean, $\mu$ .
• the population standard deviation, $\sigma$ .
• the weight that is 2 standard deviations below the mean.
• When Steve Young, quarterback, played football, he weighed 205 pounds. How many standard deviations above or below the mean was he?
• That same year, the mean weight for the Dallas Cowboys was 240.08 pounds with a standard deviation of 44.38 pounds. Emmit Smith weighed in at 209 pounds. With respect to his team, who was lighter, Smith or Young? How did you determine your answer?
• 241
• 205.5
• 272.5
• 205.5, 272.5
• sample
• population
• 236.34
• 37.50
• 161.34
• 0.84 std. dev. below the mean
• Young

Is there any normative that regulates the use of silver nanoparticles?
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
why we need to study biomolecules, molecular biology in nanotechnology?
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
why?
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
research.net
kanaga
sciencedirect big data base
Ernesto
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
how did you get the value of 2000N.What calculations are needed to arrive at it
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Berger describes sociologists as concerned with
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