L22IntroHypothesisTesting

L22IntroHypothesisTesting - MGT 2250 —— Lesson 22...

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Unformatted text preview: MGT 2250 —— Lesson 22 Introduction to Hypothesis Testing July 21, 2011 ‘ Definition: Hypothesis: 1. A tentative explanation for an observation, phenomenon, or scientific problem that can be tested by further investigation. 2. Something taken to be true for the purpose of argument or investigation; an assumption. 1.) Two competing hypotheses are proposed. a.) The Null Hypothesis The hypothesis to be tested. Represents the “status quo” —— no difference. Always includes the eguaiity. This hypothesis is either rejected 6mm. %[ 6/17 6X” fl“; Pia/FEM ,o " ——- M u s L A lief/1 "‘ X SWM WII‘U‘ p .. * L. p Ho ‘ /‘ 2: K b.) The Alternative (Research) Hypothesis Represents a “difference”. This hypothesis is accepted only if the Null hypothesis can be rejected. Always is expressed as an inequality, never include a an e ualitv’. ., u (jab: /‘ 7 A\< Ha;- /A 4" f, Ha; # # k Since these are competing hypotheses, oniy one can he accepted. if we reject Ho we must accept Ha. lfwe don’t reject Ho, we can’t accept Ha. W L22lntroHypothesisTesting - l — 2.) Examples of hypothesis tests a.) b.) Research: An automaker’s Model “A” averages 24 mpg. They want to increase the mileage, so they install a new fuel injection system on 100 of these cars. After a period of having these cars driven, they measure the mpg on them to see if there has been an increase. [fill/Q: flfig‘f Testing a claim: Orange juice cartons say they contain 32 ounces. Consumer protection tests a sample of them to determine if they actually contain less than 32 ounces. Flo‘fl 331 Haj/4 432 Quality control: Parts for a machine must be 2 inches long. If they are longer or shorter, they are rejected. Mos/L 1Q Harem L22 lntroH ypoth esisTestin g 3.) Types of Hypothesis Tests 21.) One—tail U per (l-T—U) LZZIHH‘OHypotheSisTesting 4.) Potential errors a.) Type I We reject H0 when we shouldn’t. We “find” a difference that isn’t really there. Alpha (<7< ) = Level of Significance = Probability of making a Type I error. wf {34‘ (x, lob/5%: (0% 4 b.) Type II . ‘0 V We don’t reject Ho when we should. we don’t “find” a difference that really is there. Beta (/5 ) = Probability of making a Type 11 error. U %2 {g Qéflfip/Dtéiwr Did 2X ( £< ’2 c.) Error Table (l {p OK [\ [+0 l H0 } fi‘ raw F/Nfi ] (me r-~ (9.53:: ' H QC J l \7‘ 66 [H J Fiflbm jot/VT :rT’K’L‘pfi 1:1: l w (+9 J Corleeef finite/L; \_ ‘ 1 a l . L22lntroliypothesiSTcsting ...
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This note was uploaded on 02/05/2012 for the course MGT 2250 taught by Professor Milne during the Summer '08 term at Georgia Tech.

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L22IntroHypothesisTesting - MGT 2250 —— Lesson 22...

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