This preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: 1 Assignment • After this lecture, start Assignment #4. – It’s in the course binder. 2 Compared to what? Lecture 10 Hypothesis test for a mean 3 Overview • What is a hypothesis? • How do you compare a hypothesis to your data – using confidence intervals – using sampling distributions 4 1. What is a hypothesis? 5 What is a hypothesis? • Hypothesis = Claim about a parameter – Today: claim about the population mean μ Y . • E.g., the average starting salary of all sociology BAs • Two alternatives: – null hypothesis (H ) • a neutral claim – research hypothesis (H 1 ) • onetailed or twotailed 6 Twotailed hypotheses • Does journaling affect depression • Effect has two possible directions – Journaling works through issues depression lifts – Journaling dwells on problems depression deepens • Let μ Y be average change in depression after journaling. • Null hypothesis: journaling does not affect depression H : μ Y = 0 • Research hypothesis: journaling affects depression : 1 ≠ Y H μ 7 Onetailed hypotheses • Do smokers have lighter babies? – Expected effect has one direction • In general population, – average birthweight is say 7 pounds • Let μ Y be average weight of smokers’ children. • Research hypothesis: smokers have lighter babies – H 1 : μ Y < 7 • Null hypothesis: smokers have average babies (or even heavy babies) – H : μ Y = 7 (or H : μ Y >= 7) • both forms are useful 8 One tail or two? • Key: Does the research hypothesis specify direction? • One tail – H 1 : μ Y < 7 – H : μ Y = 7 (or H : μ Y >= 7) • Two tails : : 1 = ≠ Y Y H H μ μ 9 2. Hypothesis tests 10 Hypothesis test: Definition • Given evidence from a sample , – we test (decide whether to reject) – the null hypothesis – about the population 11 Research question • Should you finish college? • Should you delay graduation for parttime work? • UPS offers $9 an hour plus $3000 a year for books and tuition $9/hour X 2000 hours/year + $3000 = $21,000 per year • Will you do better than that when you graduate? 12 Null vs. research hypothesis: Symbols • Let Y be the starting salary for a sociology BA 2200 μ Y is the average for the population of sociology BAs • H 1 : μ Y > $21K – The average is more than what you could make at UPS....
View
Full
Document
This document was uploaded on 06/01/2011.
 Spring '09

Click to edit the document details