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

Pakistani Currency

SAT Vocabulary List

 

Word list 01

Group 1

Abhor	hate
Bigot	narrow-minded, prejudiced person
Counterfeit	fake; false
Enfranchise	give voting rights
Hamper	hinder; obstruct
Kindle	to start a fire
Noxious	harmful; poisonous; lethal
Placid	calm; peaceful
Remuneration	payment for work done
Talisman	lucky charm

Group 2

Abrasive	rough; coarse; harsh
Bilk	cheat; defraud
Covert	hidden; undercover
Engender	cause
Hangar	storage area (like garage) for a plane
Knotty	complex; difficult to solve
Nuance	something subtle; a fine shade of meaning
Plagiarism	taking credit for someone else's writing or ideas
Renown	fame
Tangent	going off the main subject

Group 3

Abasement	humiliation; degradation
Billowing	swelling; fluttering; waving
Cower	recoil in fear or servility; shrink away from
Enhance	improve; make better or clearer
Harangue	noisy, attacking speech
Labyrinth	a maze
Nullify	to counter; make unimportant
Plaintiff	petitioner (in court of law)
Replete	full
Tangible	can be touched

Group 4

Abrogate	cancel; deny; repeal
Blasphemy	speech which offends religious sentiments
Credible	believable
Enigma	puzzle; mystery
Harbingers	indicators; bringers of warnings
Labyrinthine	complicated; highly convoluted
Nuzzle	cuddle; snuggle
Plaudit	statement giving strong praise
Reprehensible	shameful; very bad
Tardy	slow; late; overdue; delayed

Group 5

Absolution	forgiveness; pardon; release
Blatant	obvious
Creditable	praiseworthy
Ensconce	establish firmly in a position
Hasten	hurry; accelerate; rush
Laceration	a cut
Obdurate	stubborn
Plausible	can be believed; reasonable
Reprieve	a respite; postponement of a sentence
Tawdry	of little value; gaudy

Group 6

Abstain	desist; go without; withdraw
Blighted	damaged; destroyed; ruined
Credulous	gullible; ready to believe anything
Enshroud	cover
Haughtiness	arrogance; pride
Lachrymose	tearful; sad
Obfuscate	deliberately make something difficult to understand
Plethora	an excess
Repudiate	shun; eschew
Tedium	boredom

Group 7

Abstemious	self denying; refraining from indulging
Blithe	free-spirited; carefree
Crepuscular	active at dawn and dusk
Enunciation	clear pronunciation; accent; articulation
Headstrong	stubborn; willful
Lackluster	dull; monotonous; bland
Objective	unbiased; not subjective
Pliable	flexible; not stubborn
Rescind	retract; repeal
Temper	to moderate; soften

Group 8

Abstruse	difficult to understand; obscure
Blunderbuss	1. ancient weapon (type of gun); 2. a clumsy person
Cringe	recoil; flinch; shy away
Envenom	to cause bitterness and bad feeling
Hedonism	self indulgence; pleasure-seeking
Laconic	using few words; brief; to the point
Oblique	indirect; slanting
Plumage	feathers of a bird
Resignation	acceptance of fate
Tenacious	stubborn; resolute; holding firm to a purpose

Group 9

Accolade	tribute; honor; praise
Bolster	support; prop up
Cryptic	puzzling; enigmatic
Ephemeral	short-lived
Hedonist	a pleasure seeker
Lamentation	expression of regret or sorrow
Obliterate	destroy; demolish; eradicate
Plummet	fall suddenly and steeply
Resolution	determination
Tentative	not certain

Group 10

Acquiesce	to agree to; give in to
Bombast	arrogant, pompous language
Curtail	cut short
Epicure	someone who appreciates good food and drink
Heed	listen to
Lampoon	ridicule; spoof
Oblivious	totally unaware
Podium	raised platform
Resonant	echoing
Tenuous	flimsy; not solid Word list 02 Group 1 Acrid sharp; pungent (used of smells and tastes) Boorish ill-mannered Cynical believing that people act only out of selfish motives Epistle a letter (form of communication) Heresy against orthodox opinion Lance spear; spike; javelin Obscure difficult to understand; partially hidden Poignant deeply moving; strongly affecting the emotions Respite a break; intermission Terse concise; to the point Back to top Group 2 Acrophobia fear of heights Bourgeois middle class Debility weakness; incapacity Epistolary concerned with letters; through correspondence Hiatus interruption; pause Languid tired; slow Obscured hidden; covered; buried Poised calm; collected; self-possessed Resplendent shining; glowing Therapeutic medicinal; curative Back to top Group 3 Acuity sharpness (mental or visual) Braggart someone who boasts Debunking exposing false claims or myths Epitomized typified; characterized; personified Hidebound rigid in opinions Languish decay; fade away; get weaker Obsequious servile; submissive Polemical causing debate or argument Restorative a tonic Thwart prevent; frustrate Back to top Group 4 Adamant forceful; inflexible Brawny muscular Decathlon an athletic competition with ten events Equivocate speak ambiguously; avoid telling the truth Hieroglyphics 1. picture writing; 2. writing which is difficult to read or enigmatic Larceny theft; robbery; stealing Obsession a dominating concern Ponderous weighty; slow and heavy Retention preservation; withholding Timorous cowardly; fearful Back to top Group 5 Adroit skilful Brevity being brief Decorum dignified, correct behavior [decorous (a)] Err make a mistake Hinder obstruct Largess generosity Obsolete no longer valid Pontificate speak pompously or dogmatically Reticent restrained; holding something back; uncommunicative Tirade stream of verbal abuse Back to top Group 6 Adulation strong admiration; worship Bristle to show irritation Decoy lure; trap; trick Erratic wandering; irregular Histrionic theatrical; exaggerated Laud praise Obstreperous noisy and boisterous Portend foretell Retraction withdrawal; cancellation of a statement Titter giggle quietly Back to top Group 7 Adversity hardship Broach start to discuss; approach Deference respect Esoteric obscure and difficult to understand Hoary old Lavish on a grand scale; wasteful Obtuse mentally dull Portent a warning sign; omen Revere worship Tome large book Back to top Group 8 Advocate support Brusque blunt; abrupt Defoliate cause leaves to fall off Espouse promote; take up; support Hone sharpen; increase; whet Lax careless; not strict Obviate avoid; make unnecessary Poseur someone who puts on an act Riddled full of (usually full of holes) Torpid inactive; lazy; stagnant Back to top Group 9 Aesthetic concerning art or beauty Bulwark fortification; barricade; wall Defunct no longer in existence Etymology the study of word origins Hyperbole grossly exaggerated speech Legend 1. key to map; 2. myth or story Odious hateful Posterity future generations Rife common Torpor dormancy; sluggishness; inactivity Back to top Group 10 Affable friendly; social; easygoing Bureaucracy officialdom Degradation deprivation; poverty; debasement Eulogy praise Hypochondriac a person obsessed with health; having imaginary illnesses Legion in large numbers Officious domineering; intrusive; meddlesome Posthumous after death Rigor thoroughness Totter walk unsteadily Word list 03 Group 1 Alacrity eagerness; enthusiasm; quickness Burgeon grow; flourish; put forth new shoots Deleterious harmful Euphemism a polite phrase to cover something unpleasant Hypocritical insincere Lethargic tired; without energy Ogle stare at; observe in an obvious manner Postulate hypothesize; propose Robust strong; healthy; tough Tractable obedient; dutiful; polite Back to top Group 2 Alchemy medieval chemistry; attempt to change base metal into gold Burnish polish Deliberate to think over deeply Euphony pleasant sounds Iconoclast person who opposes orthodoxy Levity flippancy; joking about serious matters Olfactory concerned with the sense of smell Potable suitable for drinking Rotund round Tranquil peaceful Back to top Group 3 Alibi an excuse that shows someone was not at a crime scene Buttress strengthen; support Delineation demarcation; explanation; definition; outlining Evacuate vacate; empty; abandon Idiosyncrasy a personal peculiarity; something unique to an individual Libertarian someone who opposes tyranny Ominous threatening Potent powerful; compelling; strong Ruminate think over something; ponder Transcribe copy Back to top Group 4 Allay to lessen Byline the line that tells you who wrote an article Demur hesitate; refuse Exacerbate make worse Ignominious shameful Liniment soothing lotion Omnipotent all-powerful Pragmatic practical Ruse trick; stratagem Transgress go astray; disobey; commit a sin Back to top Group 5 Alleviate make less severe Cacophony discordant loud noises Denounce condemn; speak out against Exasperated frustrated; annoyed Ignominy shame [ignominious (a) = shameful] Lithe flexible; supple Omniscient all-knowing Pragmatist practical person; one who is concerned with usefulness Saccharin falsely sweet Transient short-lived; ephemeral Back to top Group 6 Aloof distant; detached; cold Cajole coax Deplete use up; lessen Exceptionable very bad (something which we should object to) Illuminate to light up or make clear Livid very angry Onerous burdensome; hard to undertake Preamble introductory material Sacrosanct very holy; inviolable Traverse to move across Back to top Group 7 Altruism putting others first; being self-sacrificing Caldron huge cooking pot Deplore regret Exculpate free someone from blame; pardon; acquit Illusory deceptive; false; misleading Lobbyist person who tries to persuade someone to support a particular cause Onus burden Precarious unstable; risky Sagacious wise Trepidation fear Back to top Group 8 Amass accumulate Callow immature Depravity moral corruption Execrable very, very bad Immoderate excessive; extreme Lofty snooty; arrogant; haughty Opaque does not let light through Precedent a previous occurrence used as a guide Sage a wise person Trinket something of little value; knick-knack Back to top Group 9 Ambiguity uncertainty; vagueness Candid frank; honest Deprecate criticize; denounce Exegesis scholarly explanation or interpretation Immutable unchanging; permanent Longevity long life Opulent wealthy; rich; magnificent Precept guiding principle Salacious lecherous; erotic Trite unoriginal; dull Back to top Group 10 Ambiguous unclear in meaning; can be interpreted in different ways Candor frankness; openness Deride ridicule; make fun of; mock Exemplary outstandingly good; setting a fine example Impartial unbiased; neutral Loquacious talkative Ordain 1. destine; 2. confer holy orders on a priest Precinct district of a city Sallow yellowish Trivial unimportant

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.

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SAT Vocabulary

Selected 1000 words    - Click Blog Page

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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 () 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

 

 

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.

• Revisiting Numbers with Shakuntala Devi -Watch 

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
  
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  Figuring: The Joy of Numbers

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