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References

Cauchon, Dennis, Paul Overberg. “Census data shows minorities now a majority of U.S. births.” USA Today, 2012. Available online at http://usatoday30.usatoday.com/news/nation/story/2012-05-17/minority-birthscensus/55029100/1 (accessed April 3, 2013).

Data from the United States Department of Commerce: United States Census Bureau. Available online at http://www.census.gov/ (accessed April 3, 2013).

“1990 Census.” United States Department of Commerce: United States Census Bureau. Available online at http://www.census.gov/main/www/cen1990.html (accessed April 3, 2013).

Data from San Jose Mercury News .

Data from Time Magazine ; survey by Yankelovich Partners, Inc.

Chapter review

The values that divide a rank-ordered set of data into 100 equal parts are called percentiles. Percentiles are used to compare and interpret data. For example, an observation at the 50 th percentile would be greater than 50 percent of the other obeservations in the set. Quartiles divide data into quarters. The first quartile ( Q 1 ) is the 25 th percentile,the second quartile ( Q 2 or median) is 50 th percentile, and the third quartile ( Q 3 ) is the the 75 th percentile. The interquartile range, or IQR , is the range of the middle 50 percent of the data values. The IQR is found by subtracting Q 1 from Q 3 , and can help determine outliers by using the following two expressions.

  • Q 3 + IQR (1.5)
  • Q 1 IQR (1.5)

Formula review

i = ( k 100 ) ( n + 1 )

where i = the ranking or position of a data value,

k = the kth percentile,

n = total number of data.

Expression for finding the percentile of a data value: ( x  +  0.5 y n ) (100)

where x = the number of values counting from the bottom of the data list up to but not including the data value for which you want to find the percentile,

y = the number of data values equal to the data value for which you want to find the percentile,

n = total number of data

Listed are 29 ages for Academy Award winning best actors in order from smallest to largest.

18; 21; 22; 25; 26; 27; 29; 30; 31; 33; 36; 37; 41; 42; 47; 52; 55; 57; 58; 62; 64; 67; 69; 71; 72; 73; 74; 76; 77

  1. Find the 40 th percentile.
  2. Find the 78 th percentile.
  1. The 40 th percentile is 37 years.
  2. The 78 th percentile is 70 years.
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Listed are 32 ages for Academy Award winning best actors in order from smallest to largest.

18; 18; 21; 22; 25; 26; 27; 29; 30; 31; 31; 33; 36; 37; 37; 41; 42; 47; 52; 55; 57; 58; 62; 64; 67; 69; 71; 72; 73; 74; 76; 77

  1. Find the percentile of 37.
  2. Find the percentile of 72.
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Jesse was ranked 37 th in his graduating class of 180 students. At what percentile is Jesse’s ranking?

Jesse graduated 37 th out of a class of 180 students. There are 180 – 37 = 143 students ranked below Jesse. There is one rank of 37.

x = 143 and y = 1. x + 0.5 y n (100) = 143 + 0.5 ( 1 ) 180 (100) = 79.72. Jesse’s rank of 37 puts him at the 80 th percentile.

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  1. For runners in a race, a low time means a faster run. The winners in a race have the shortest running times. Is it more desirable to have a finish time with a high or a low percentile when running a race?
  2. The 20 th percentile of run times in a particular race is 5.2 minutes. Write a sentence interpreting the 20 th percentile in the context of the situation.
  3. A bicyclist in the 90 th percentile of a bicycle race completed the race in 1 hour and 12 minutes. Is he among the fastest or slowest cyclists in the race? Write a sentence interpreting the 90 th percentile in the context of the situation.
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  1. For runners in a race, a higher speed means a faster run. Is it more desirable to have a speed with a high or a low percentile when running a race?
  2. The 40 th percentile of speeds in a particular race is 7.5 miles per hour. Write a sentence interpreting the 40 th percentile in the context of the situation.
  1. For runners in a race it is more desirable to have a high percentile for speed. A high percentile means a higher speed which is faster.
  2. 40% of runners ran at speeds of 7.5 miles per hour or less (slower). 60% of runners ran at speeds of 7.5 miles per hour or more (faster).
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On an exam, would it be more desirable to earn a grade with a high or low percentile? Explain.

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Mina is waiting in line at the Department of Motor Vehicles (DMV). Her wait time of 32 minutes is the 85 th percentile of wait times. Is that good or bad? Write a sentence interpreting the 85 th percentile in the context of this situation.

When waiting in line at the DMV, the 85 th percentile would be a long wait time compared to the other people waiting. 85% of people had shorter wait times than Mina. In this context, Mina would prefer a wait time corresponding to a lower percentile. 85% of people at the DMV waited 32 minutes or less. 15% of people at the DMV waited 32 minutes or longer.

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In a survey collecting data about the salaries earned by recent college graduates, Li found that her salary was in the 78 th percentile. Should Li be pleased or upset by this result? Explain.

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In a study collecting data about the repair costs of damage to automobiles in a certain type of crash tests, a certain model of car had $1,700 in damage and was in the 90 th percentile. Should the manufacturer and the consumer be pleased or upset by this result? Explain and write a sentence that interprets the 90 th percentile in the context of this problem.

The manufacturer and the consumer would be upset. This is a large repair cost for the damages, compared to the other cars in the sample. INTERPRETATION: 90% of the crash tested cars had damage repair costs of $1700 or less; only 10% had damage repair costs of $1700 or more.

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The University of California has two criteria used to set admission standards for freshman to be admitted to a college in the UC system:

  1. Students' GPAs and scores on standardized tests (SATs and ACTs) are entered into a formula that calculates an "admissions index" score. The admissions index score is used to set eligibility standards intended to meet the goal of admitting the top 12% of high school students in the state. In this context, what percentile does the top 12% represent?
  2. Students whose GPAs are at or above the 96 th percentile of all students at their high school are eligible (called eligible in the local context), even if they are not in the top 12% of all students in the state. What percentage of students from each high school are "eligible in the local context"?
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Suppose that you are buying a house. You and your realtor have determined that the most expensive house you can afford is the 34 th percentile. The 34 th percentile of housing prices is $240,000 in the town you want to move to. In this town, can you afford 34% of the houses or 66% of the houses?

You can afford 34% of houses. 66% of the houses are too expensive for your budget. INTERPRETATION: 34% of houses cost $240,000 or less. 66% of houses cost $240,000 or more.

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Use [link] to calculate the following values:

First quartile = _______

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Second quartile = median = 50 th percentile = _______

4

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Third quartile = _______

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Interquartile range ( IQR ) = _____ – _____ = _____

6 – 4 = 2

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10 th percentile = _______

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70 th percentile = _______

6

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Questions & Answers

If X is a Uniform random variable in [ -2, 2 ], find the pdf of Y X  and E Y[ ].
Kezang Reply
I want to know statistics
Okosa Reply
why is data so important in statistics
Trixie Reply
want summary statistic on gender, age group, weight, and weight loss
Trixie
are you asking question or looking for Solution
Arun
solution pls
Trixie
1st convert gender and group to factor than use summary function It will give mean median and mode with other details
Arun
its a bit complicated could u bring it to my level of under standing
Trixie
u know the question was put in a tabular form where we were to find the variable type, summary statistics and graph type of the given variables that's the gender,age group, weight and weight loss
Trixie
if you see, gender and group are not numerical due to which they will not give you correct statistics
Arun
how you denote gender m or f
Arun
or t
Arun
ok tnk u
Trixie
these are not numerical so you have to convert they as f=1; m=2; t=3 same thing you have to do with group or any variable which is character else you should drop them
Arun
from your calculation
Arun
oh OK tnk u
Trixie
so pls why is data important in statistics
Trixie
not only data correct data is imp
Arun
statistics works on data only
Arun
without data you can not summarize, can not predict future, can not establish relationship between two and more variables, can not prepare reports and make decisions on it
Arun
so I'll give example. suppose you want to open a restaurant and you have to choose one best location out of 5. then how you will decide which location is best for you
Arun
awww thank you pls
Trixie
pls I want a brief note on observation, survey and experimentation way of obtaining data
Trixie
hi
Abdiwahab
please Tell me difference parameters and non parameter
Abdiwahab
can you tell me about the scopes of statistics?
Minhal
plzzz answer me anyone .
Minhal
Methods of Collecting Data Observation Observational studies allow researchers to document behavior in a natural setting and witness events that could not be produced in a lab.
Arun
Key Points Observation differs from most other forms of data collection in that the researcher does not manipulate variables or directly question participants. The advantages of observation include observing natural behavior, refining hypotheses, and allowing for observation of behavior that canno
Arun
 be produced in an artificial environment for ethical or practical reasons. The disadvantages of observation are that these studies do not produce quantitative data, do not allow for cause and effect statements, may be very time consuming, and can be prone to researcher bias.
Arun
Key Terms observational research: Research focusing on the observation of behavior outside of a laboratory setting. external validity: In research, whether or not study findings can be generalized to real world scenarios.
Arun
Surveys and Interviews Surveys are a low-cost option for gathering a large amount of data, but they are also susceptible to reporting bias.
Arun
Key Points The survey method of data collection is likely the most common of the four major research methods. The benefits of this method include low cost, large sample size, and efficiency.
Arun
The major problem with this method is accuracy: since surveys depend on subjects’ motivation, honesty, memory, and ability to respond, they are very susceptible to bias. A researcher must have a strong understanding of how to properly frame survey questions in order to gather reliable and relevant
Arun
Key Terms reliability: The degree to which a measure is likely to yield consistent results each time it is used. validity: The degree to which a measure is actually assessing the concept it was designed to measure. survey: A method for collecting qualitative and quantitative information about ind
Arun
individuals in a population.
Arun
Interviews Interviews are a type of qualitative data in which the researcher asks questions to elicit facts or statements from the interviewee. Interviews used for research can take several forms:
Arun
Informal Interview: A more conversational type of interview, no questions are asked and the interviewee is allowed to talk freely. General interview guide approach: Ensures that the same general areas of information are collected from each interviewee. Provides more focus than the conversational ap
Arun
approach, but still allows a degree of freedom and adaptability in getting the information from the interviewee. Standardized, open-ended interview: The same open-ended questions are asked to all interviewees. This approach facilitates faster interviews that can be more easily analyzed and compared
Arun
Closed, fixed-response interview (Structured): All interviewees are asked the same questions and asked to choose answers from among the same set of alternatives.
Arun
experiments An experiment involves the creation of a contrived situation in order that the researcher can manipulate one or more variables whilst controlling all of the others and measuring the resultant effects.
Arun
Boyd and Westfall1 have defined experimentation as: "...that research process in which one or more variables are manipulated under conditions which permit the collection of data which show the effects, if any, in unconfused fashion."
Arun
Experiments can be conducted either in the field or in a laboratory setting. When operating within a laboratory environment, the researcher has direct control over most, if not all, of the variables that could impact upon the outcome of the experiment
Arun
When experiments are conducted within a natural setting then they are termed field experiments. The variety test carried out by United Fruits on their Gros Michel and Valery bananas is an example of a field experiment.
Arun
parameter Parameters are factors or limits which affect the way that something can be done or made
Arun
Minhal didny get your question, can you please elaborate more
Arun
pls can u use mean n mode at the statistical summary pls
Trixie
yes, statistical summary itself gives all value
Arun
but u didn't tell me the advantage and disadvantage of the experimental method
Trixie
but you didn't tell me the advantage and disadvantage of experimental method
Trixie
by using a sampling distribution? how to estimate the population mean using a ramdom variable n?
Jade Reply
The “average increase” for all NASDAQ stocks is the:
da Reply
any video any proof...what is point of estimation in statistics
Younis Reply
Define the meaning of statistics
Robert Reply
sampli
Hidayat
roductory Statistics is intended for the one-semester introduction to statistics course for students who are not mathematics or engineering majors. It focuses on the interpretation of statistical results, especially in real world settings, and assumes that students have an understanding of intermedi
Hidayat
statistics is science collection of method planning experiment then organizing summarizing presenting analyzing and drawing conclusion.
MOVIES
uses and miss uses of statistics
Pure
Identify the population, sample, parameter, statistic, variable, and data for this example. population sample parameter statistic variable data
Woyo
kinds of probability samples and there advantage
Hajira Reply
are you going to explain it.
Anil
🙂
Meera
hy
Muhammad
what....?
Muhammad
Sampling takes on two forms in statistics: probability sampling and non-probability sampling: Probability sampling uses random sampling techniques to create a sample. Non-probability samplingtechniques use non-random processes like researcher judgment or convenience sampling.
Muhammad
Advantages Cluster sampling: convenience and ease of use. Simple random sampling: creates samples that are highly representative of the population. Stratified random sampling: creates strata or layers that are highly representative of strata or layers in the population. Systematic sampling: creates
Muhammad
any example plz?
Anil
Plz write the uses and miss uses of statistical theory
Pure
what is the difference between weighted simple price index (WSPI ) & Laspeyre's Price Index ( LPI )
Basil Reply
What are the 5 steps of hypothesis testing?
Sixolisiwe Reply
5 steps of hypothesis testing
Sixolisiwe
Make guesses (e.g., customers will leave if we raise our rates) State the null H0 and alternative H1 hypotheses (e.g., H0: there is no correlation) and alpha Select the sampling distribution and specify the test statistic Compute the test statistic Make a decision and interpret the results
Ara
.Five Steps in Hypothesis Testing: 1_Specify the Null Hypothesis. 2_Specify the Alternative Hypothesis. 3_Set the Significance Level (a) 4_Calculate the Test Statistic and Corresponding P-Value. 5_Drawing a Conclusion.
Rachel
.Econometric Results uses Multiple Regression for the basis of looking at number of casual factors (independent χ Variables) such as Employment, being Female etc., to test for any relationship with the dependent γ Variable Wages, in order to find any evidence to support the Alternative Hypothesis(Ha
Rachel
.Alternative Hypothesis (H1 or Ha) of Wage Differentials or in the extreme case, if the strength of relationship is strong enough between the dependent γ Variable, and multiple χ Variables, suggesting evidence for the Null Hypothesis ( Ho) that Wage Discrimination may exist.
Rachel
.The Significance Level which is also the Critical Value gives the maximum allowable probability of making a Type I error – the Significance Level value of which is decided upon before the data sample is collected and analysed, as a guide to avoid or control making a Type I error.
Rachel
Type I Error occurs when the Null Hypothesis (Ho) is not accepted when in reality the Null Hypothesis is true. A Type II Error however, occurs when one fails to reject the Null Hypothesis when in reality, the Null Hypothesis (Ho) is not true.
Rachel
.The #P-Value measures the likelihood of getting the sample results if the Null Hypothesis were true, and could be defined as the smallest level of significance (observed level of significance) at which the Null Hypothesis will be rejected, assuming the Null Hypothesis (Ho) is true.
Rachel
.In most cases, the research attempt is to find support for the Alternative Hypothesis (Ha or H1). Thus, the smaller the P-Value, the more the (the father out the #Test-Statistics is on the Standard Normal Distribution Diagram, and the more confident the researcher can be about rejecting the Null H
Rachel
.#Test-Statistics is on the Standard Normal Distribution Diagram, and the more confident the researcher can be about rejecting the Null Hypothesis (Ho) in support for the Alternative Hypothesis (H1 / Ha).
Rachel
.The #P-Value is less than the Critical Values (Significance Level) of 1% (0.01), 5% (0.05), and 10% (0.10) given in Table (1) in the Appendix, means the Null Hypothesis (Ho) that there is Wage Discrimination is not reflective of the population or equal to the Mean of the Population
Rachel
.Mean of the Population(data sample of Sample Mean distribution of the Population ) which confirms that the Researcher Rejects the Null Hypothesis (Ho) and Accepts the (Alternative Hypothesis).
Rachel
.See ISBN 1537512757 ; link : https://smile.amazon.co.uk/Winston-Chellie-Economics-TheBachelor-questions/dp/1537512757/ref=mp_s_a_1_1?keywords=Rachel+Adeniji&qid=1572318698&sr=8-1
Rachel
see publication ' Winston and Chellie by Rachel Adeniji '
Rachel
correction, dependent x variables such as Employment, being Female; dependent y variable Wages
Rachel
correction, Wage Differentials such as Employment, Region affecting Wages; Wage Discrimination such as being Female or Ethnicity affecting Wages
Rachel
correction_, linear regression/equation is computed as y=mx + c or y=m • x1+x2+x3+c where independent x variables eg Employment x1, Female x2 , Ethnicity x3, and dependent y variable Wages
Rachel
how do you draw a line of best fit?
Josh Reply
***youtu.be/l2BOZDosuIk
William
informal explanation:lets suppose you have 10 points and you want a line to best fit on all of them. all you need to keep in mind that the distance and error should be minimum and you will get the best fit line.
umair
how was the data collected to draw the graph
Nji
draw a straight line through the points on the graph that are most clustered with other data / points
Rachel
suppose that 30% of the employees in a large factory of smokers what is the probability that there will be exactly two smokers in a randomly-chosen five-person workgroup
rayhaanah Reply
binomialPdf(5, .3, 2) .3087
Ara
are the fraction integers
Amir Reply
The ratio of male to female nurses is 2:3 or 2/3. There are 40 nurses in the ward. For every 5 nurses, how many male and female nurses are there? How many groups can be divided into shifts. Pls show the solution and explain.
DokBads Reply
in a group of 5, the probability tbat exactly 3 of the nurses are male is .6630 or 66% calculation P(X=0)+(...)+P(X=3)=.6630
Ara
i dont think u got a correct answer. you are computing for the probability not the ratio and proportion
DokBads
(2+5)/40*2 = male , (2+5)/40*3 = female
Rachel
40/(2+3)*2 = male , 40/(2+3)*3=female, ....sorry correction
Rachel
thank you so much for the help
DokBads
x
Rachel
Iyhoo
Sixolisiwe
if x is a continuous random variable and` c` is a constant then p(x=c)
Neha Reply
the length of human pregnancies from conception to birth approximates a normal distribution with a mean of 266days and a standard deviation of 16days.(i) what length of time marks the shortest 10%of all pregnancies ?
Neha
27.6390625 days
festus
steps?
Neha
how can I solve a Hypothetic problem that provide sample data such as 45,3_,45,28,17 ect...what is the first step
Leticia
find the mean and standard deviation first
Kwadwo
how can I get line of best fit?
Josh

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Source:  OpenStax, Introductory statistics. OpenStax CNX. May 06, 2016 Download for free at http://legacy.cnx.org/content/col11562/1.18
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