Friday 29 June 2012

Stratified sampling

Stratified sampling

Stratification is the process of dividing members of the population into homogeneous subgroups before sampling.

The strata should be mutually exclusive and collectively exhaustive

Then simple random sampling or systematic sampling is applied within each stratum.

It can produce a weighted mean that has less variability than the arithmetic mean of a simple random sample of the population. 

In computational statistics, stratified sampling is a method of variance reduction when Monte Carlo methods are used to estimate population statistics from a known population.

BOOK: Strategic Management

Strategic Management - Concepts and Cases - 13th Edition 2011 ( Fred R. Devid)











Read 

Virus and a Worm

Difference between a Virus and a Worm?

“Virus” has become a generic term that includes all the malicious ways your computer can be attacked.   

Viruses are distributed by making copies of themselves or replication.   

Sometimes the replication itself causes damage to your hard disk.  Sometimes the accumulative effect of replicating again and again disables the computer. 

A Virus is a program that piggy-backs on other programs. It can be attached to a Word or Excel file.  Each time the file is run, the virus runs too.  It attaches itself to other programs and continues to reproduce.

An Email virus is a special type of virus sent as an attachment to an email message.  It replicates by automatically mailing itself to everyone in the recipients email address book.  

A Worm uses computer networks to replicate itself.  It searches for servers with security holes and copies itself there.  It then begins the search and replication process again.

A Trojan Horse is a computer program masquerading as a game or a “cute” program.  However, when it runs it does something else - like erasing your hard drive or blocking your screen with a graphic will not go away.
Some viruses use several of these in combination to replicate themselves

Tuesday 26 June 2012

SAT Vocabulary List

SAT Vocabulary List

 

Word list 01

Group 1


Abhorhate
Bigotnarrow-minded, prejudiced person
Counterfeitfake; false
Enfranchisegive voting rights
Hamperhinder; obstruct
Kindleto start a fire
Noxiousharmful; poisonous; lethal
Placidcalm; peaceful
Remunerationpayment for work done
Talismanlucky charm

Group 2


Abrasiverough; coarse; harsh
Bilkcheat; defraud
Coverthidden; undercover
Engendercause
Hangarstorage area (like garage) for a plane
Knottycomplex; difficult to solve
Nuancesomething subtle; a fine shade of meaning
Plagiarismtaking credit for someone else's writing or ideas
Renownfame
Tangentgoing off the main subject

Group 3


Abasementhumiliation; degradation
Billowingswelling; fluttering; waving
Cowerrecoil in fear or servility; shrink away from
Enhanceimprove; make better or clearer
Haranguenoisy, attacking speech
Labyrintha maze
Nullifyto counter; make unimportant
Plaintiffpetitioner (in court of law)
Repletefull
Tangiblecan be touched

Group 4


Abrogatecancel; deny; repeal
Blasphemyspeech which offends religious sentiments
Crediblebelievable
Enigmapuzzle; mystery
Harbingersindicators; bringers of warnings
Labyrinthinecomplicated; highly convoluted
Nuzzlecuddle; snuggle
Plauditstatement giving strong praise
Reprehensibleshameful; very bad
Tardyslow; late; overdue; delayed

Group 5


Absolutionforgiveness; pardon; release
Blatantobvious
Creditablepraiseworthy
Ensconceestablish firmly in a position
Hastenhurry; accelerate; rush
Lacerationa cut
Obduratestubborn
Plausiblecan be believed; reasonable
Reprievea respite; postponement of a sentence
Tawdryof little value; gaudy

Group 6


Abstaindesist; go without; withdraw
Blighteddamaged; destroyed; ruined
Credulousgullible; ready to believe anything
Enshroudcover
Haughtinessarrogance; pride
Lachrymosetearful; sad
Obfuscatedeliberately make something difficult to understand
Plethoraan excess
Repudiateshun; eschew
Tediumboredom

Group 7


Abstemiousself denying; refraining from indulging
Blithefree-spirited; carefree
Crepuscularactive at dawn and dusk
Enunciationclear pronunciation; accent; articulation
Headstrongstubborn; willful
Lacklusterdull; monotonous; bland
Objectiveunbiased; not subjective
Pliableflexible; not stubborn
Rescindretract; repeal
Temperto moderate; soften

Group 8


Abstrusedifficult to understand; obscure
Blunderbuss1. ancient weapon (type of gun); 2. a clumsy person
Cringerecoil; flinch; shy away
Envenomto cause bitterness and bad feeling
Hedonismself indulgence; pleasure-seeking
Laconicusing few words; brief; to the point
Obliqueindirect; slanting
Plumagefeathers of a bird
Resignationacceptance of fate
Tenaciousstubborn; resolute; holding firm to a purpose

Group 9


Accoladetribute; honor; praise
Bolstersupport; prop up
Crypticpuzzling; enigmatic
Ephemeralshort-lived
Hedonista pleasure seeker
Lamentationexpression of regret or sorrow
Obliteratedestroy; demolish; eradicate
Plummetfall suddenly and steeply
Resolutiondetermination
Tentativenot certain

Group 10


Acquiesceto agree to; give in to
Bombastarrogant, pompous language
Curtailcut short
Epicuresomeone who appreciates good food and drink
Heedlisten to
Lampoonridicule; spoof
Oblivioustotally unaware
Podiumraised platform
Resonantechoing
Tenuousflimsy; not solid



Word list 02

Group 1


Acridsharp; pungent (used of smells and tastes)
Boorishill-mannered
Cynicalbelieving that people act only out of selfish motives
Epistlea letter (form of communication)
Heresyagainst orthodox opinion
Lancespear; spike; javelin
Obscuredifficult to understand; partially hidden
Poignantdeeply moving; strongly affecting the emotions
Respitea break; intermission
Terseconcise; to the point
Back to top

Group 2


Acrophobiafear of heights
Bourgeoismiddle class
Debilityweakness; incapacity
Epistolaryconcerned with letters; through correspondence
Hiatusinterruption; pause
Languidtired; slow
Obscuredhidden; covered; buried
Poisedcalm; collected; self-possessed
Resplendentshining; glowing
Therapeuticmedicinal; curative
Back to top

Group 3


Acuitysharpness (mental or visual)
Braggartsomeone who boasts
Debunkingexposing false claims or myths
Epitomizedtypified; characterized; personified
Hideboundrigid in opinions
Languishdecay; fade away; get weaker
Obsequiousservile; submissive
Polemicalcausing debate or argument
Restorativea tonic
Thwartprevent; frustrate
Back to top

Group 4


Adamantforceful; inflexible
Brawnymuscular
Decathlonan athletic competition with ten events
Equivocatespeak ambiguously; avoid telling the truth
Hieroglyphics1. picture writing; 2. writing which is difficult to read or enigmatic
Larcenytheft; robbery; stealing
Obsessiona dominating concern
Ponderousweighty; slow and heavy
Retentionpreservation; withholding
Timorouscowardly; fearful
Back to top

Group 5


Adroitskilful
Brevitybeing brief
Decorumdignified, correct behavior [decorous (a)]
Errmake a mistake
Hinderobstruct
Largessgenerosity
Obsoleteno longer valid
Pontificatespeak pompously or dogmatically
Reticentrestrained; holding something back; uncommunicative
Tiradestream of verbal abuse
Back to top

Group 6


Adulationstrong admiration; worship
Bristleto show irritation
Decoylure; trap; trick
Erraticwandering; irregular
Histrionictheatrical; exaggerated
Laudpraise
Obstreperousnoisy and boisterous
Portendforetell
Retractionwithdrawal; cancellation of a statement
Tittergiggle quietly
Back to top

Group 7


Adversityhardship
Broachstart to discuss; approach
Deferencerespect
Esotericobscure and difficult to understand
Hoaryold
Lavishon a grand scale; wasteful
Obtusementally dull
Portenta warning sign; omen
Revereworship
Tomelarge book
Back to top

Group 8


Advocatesupport
Brusqueblunt; abrupt
Defoliatecause leaves to fall off
Espousepromote; take up; support
Honesharpen; increase; whet
Laxcareless; not strict
Obviateavoid; make unnecessary
Poseursomeone who puts on an act
Riddledfull of (usually full of holes)
Torpidinactive; lazy; stagnant
Back to top

Group 9


Aestheticconcerning art or beauty
Bulwarkfortification; barricade; wall
Defunctno longer in existence
Etymologythe study of word origins
Hyperbolegrossly exaggerated speech
Legend1. key to map; 2. myth or story
Odioushateful
Posterityfuture generations
Rifecommon
Torpordormancy; sluggishness; inactivity
Back to top

Group 10


Affablefriendly; social; easygoing
Bureaucracyofficialdom
Degradationdeprivation; poverty; debasement
Eulogypraise
Hypochondriaca person obsessed with health; having imaginary illnesses
Legionin large numbers
Officiousdomineering; intrusive; meddlesome
Posthumousafter death
Rigorthoroughness
Totterwalk unsteadily

Word list 03

Group 1


Alacrityeagerness; enthusiasm; quickness
Burgeongrow; flourish; put forth new shoots
Deleteriousharmful
Euphemisma polite phrase to cover something unpleasant
Hypocriticalinsincere
Lethargictired; without energy
Oglestare at; observe in an obvious manner
Postulatehypothesize; propose
Robuststrong; healthy; tough
Tractableobedient; dutiful; polite
Back to top

Group 2


Alchemymedieval chemistry; attempt to change base metal into gold
Burnishpolish
Deliberateto think over deeply
Euphonypleasant sounds
Iconoclastperson who opposes orthodoxy
Levityflippancy; joking about serious matters
Olfactoryconcerned with the sense of smell
Potablesuitable for drinking
Rotundround
Tranquilpeaceful
Back to top

Group 3


Alibian excuse that shows someone was not at a crime scene
Buttressstrengthen; support
Delineationdemarcation; explanation; definition; outlining
Evacuatevacate; empty; abandon
Idiosyncrasya personal peculiarity; something unique to an individual
Libertariansomeone who opposes tyranny
Ominousthreatening
Potentpowerful; compelling; strong
Ruminatethink over something; ponder
Transcribecopy
Back to top

Group 4


Allayto lessen
Bylinethe line that tells you who wrote an article
Demurhesitate; refuse
Exacerbatemake worse
Ignominiousshameful
Linimentsoothing lotion
Omnipotentall-powerful
Pragmaticpractical
Rusetrick; stratagem
Transgressgo astray; disobey; commit a sin
Back to top

Group 5


Alleviatemake less severe
Cacophonydiscordant loud noises
Denouncecondemn; speak out against
Exasperatedfrustrated; annoyed
Ignominyshame [ignominious (a) = shameful]
Litheflexible; supple
Omniscientall-knowing
Pragmatistpractical person; one who is concerned with usefulness
Saccharinfalsely sweet
Transientshort-lived; ephemeral
Back to top

Group 6


Aloofdistant; detached; cold
Cajolecoax
Depleteuse up; lessen
Exceptionablevery bad (something which we should object to)
Illuminateto light up or make clear
Lividvery angry
Onerousburdensome; hard to undertake
Preambleintroductory material
Sacrosanctvery holy; inviolable
Traverseto move across
Back to top

Group 7


Altruismputting others first; being self-sacrificing
Caldronhuge cooking pot
Deploreregret
Exculpatefree someone from blame; pardon; acquit
Illusorydeceptive; false; misleading
Lobbyistperson who tries to persuade someone to support a particular cause
Onusburden
Precariousunstable; risky
Sagaciouswise
Trepidationfear
Back to top

Group 8


Amassaccumulate
Callowimmature
Depravitymoral corruption
Execrablevery, very bad
Immoderateexcessive; extreme
Loftysnooty; arrogant; haughty
Opaquedoes not let light through
Precedenta previous occurrence used as a guide
Sagea wise person
Trinketsomething of little value; knick-knack
Back to top

Group 9


Ambiguityuncertainty; vagueness
Candidfrank; honest
Deprecatecriticize; denounce
Exegesisscholarly explanation or interpretation
Immutableunchanging; permanent
Longevitylong life
Opulentwealthy; rich; magnificent
Preceptguiding principle
Salaciouslecherous; erotic
Triteunoriginal; dull
Back to top

Group 10


Ambiguousunclear in meaning; can be interpreted in different ways
Candorfrankness; openness
Derideridicule; make fun of; mock
Exemplaryoutstandingly good; setting a fine example
Impartialunbiased; neutral
Loquacioustalkative
Ordain1. destine; 2. confer holy orders on a priest
Precinctdistrict of a city
Sallowyellowish
Trivialunimportant

Saturday 23 June 2012

SAT


 

All about the SAT

Your SAT score is a pivotal component of your college applications. Most colleges use these scores to help decide whether to admit students or not.


 SAT I or SAT Reasoning Test, in particular, has three major sections -
  1.  Mathematics, 
  2. Critical reading and 
  3. Writing. 

SAT II or SAT Subject Test, on the other hand, focuses on the students knowledge on a particular subject area like math, world history, chemistry, physics and others.

Critical Reading Section

The SAT I Critical Reading section was formerly known as the verbal section and was only changed to critical reading section on 2006.

It contains three critical reading subsections, two of which last for about 25 minutes while the remaining one for 20 minutes.

Lots of passages are expected to be encountered in this section. The passages are followed by questions that will test the examiners ability to read critical information.

Sentence completion problems can also be found in this section.

All in all, the Critical Reading section has 48 questions about reading passages. The passages could be either long or short and ranges from 100 to 850 words. The topics of the passages can come from social science, humanities, fiction and the sciences. However, prior knowledge on each subject is not needed. Also, some passages can be either strictly narrative or persuasive.

Sentence Completion Questions

Sentences that can be seen here may be missing one or more words

One tip to beat this section is to have a wide vocabulary and broad understanding of complicated sentences. All in all, there are 19 sentence completion questions in SAT I and it composes about one-third of the Critical Reading questions. 

Math Section

Like the Critical Reading section, Math section is divided into three subsections. Two of them are 25 minutes each while the remaining one takes 20 minutes. There are 44 multiple choice questions for this section. However, examiners must come up with their own answers in the 10 grid-in questions.

Questions in the Math section basically cover mathematical operations, geometry, algebra, statistics and interpretation of tabular and graphical data.

Essay Section

All SAT I examination begin with the Essay section. The examiners are given a topic and a time of 25 minutes to come up with a logical and clear essay. No background knowledge is required for this section.

However, the examiner must be able to create a well thought-out answer based on reasoning, good evidence and organization. To be able to beat this section, one must begin reading sample essays and practice skills like developing and outlining logical responses.

Writing Section

The SAT I Writing section is also divided into three subsections. One section is an essay section lasting for about 25 minutes and the other two sections are multiple choice sections lasting for 25 minutes and 10 minutes. The examiners are tested in this section with regards to their ability to improve writing samples, identify writing errors and produce their own logical and clear essay.

WEB


SAT Vocabulary

Selected 1000 words    - Click Blog Page

Click

  

Degrees Of Freedom

Degrees Of Freedom

 In statistics,the number of values in the final calculation of a statistic that are free to vary

Any of the unrestricted, independent random variables that constitute a statistic. 

The number of degrees of freedom is a measure of how certain we are that our sample population is representative of the entire population - 

the more degrees of freedom, usually the more certain we can be that we have accurately sampled the entire population 

For example, if you have to take ten different courses to graduate, and only ten different courses are offered, then you have nine degrees of freedom. Nine semesters you will be able to choose which class to take; the tenth semester, there will only be one class left to take - there is no choice, if you want to graduate. 

In many statistical problems we are required to determine the degrees of freedom. This refers to a positive whole number that indicates the lack of restrictions in our calculations. The degree of freedom is the number of values in a calculation that we can vary.

we suppose that we know the mean of a data set is 25, with values 20, 10, and two unknown values. These unknowns could be different, so we use two different variables, x and y to denote this. The resulting formula is (20 + 10 + x + y)/4 = 25. With some algebra we obtain y = 70 - x. The formula is written in this form to show that once we choose a value for x, the value for y is determined. This shows that there is one degree of freedom.

Student t Distribution

  When the population standard deviation (Sigma) is unknown and the sample size is less than 30 (n < 30), the distribution of the test statistic can not be guaranteed to be normal. In fact, the test statistic can be said to conform to what is called a t distribution.

Web  (purpose of df)

Chi-Square Distribution

 

 


Wednesday 20 June 2012

Shakuntala Devi

Shakuntala Devi 

Indian calculating prodigy

"Numbers have life, They are not just symbols on paper"

 Shakuntala was born on November 4, 1939 in Bangalore, India was well known Human Computer. 

In 1977 In Dallas she competed with a computer to see who give the cube root of 

188138517 faster, she won. 

At university of USA she was asked to give the 23rd root of 

91674867692003915809866092758538016248310668014430862240712651642793465704086709659 32792057674808067900227830163549248523803357453169351119035965775473400756818688305 620821016129132845564895780158806771.

She answered in 50seconds. The answer is 546372891. It took a UNIVAC 1108 computer, full one minute (10 seconds more) to confirm that she was right after it was fed with 13000 instructions.

Books

  •  Book of Numbers (New Delhi: Orient, 2006). ISBN 978-81-222-0006-5  

    • In the Wonderland of Numbers (New Delhi: Orient, 2006). ISBN 978-81-222-0399-8
    • Super Memory: It Can Be Yours (New Delhi: Orient, 2011). ISBN 978-81-222-0507-7; (Sydney: New Holland, 2012). ISBN 978-1-74257-240-6, OCLC 781171515
    • Mathability: Awaken the Math Genius in Your Child (New Delhi: Orient, 2005). ISBN 978-81-222-0316-5
    • Astrology for You (New Delhi: Orient, 2005). ISBN 978-81-222-0067-6

    Book: Read

    Figuring: The Joy of Numbers

    Puzzle to Puzzle 

    Solutions