STAT 2507A &acirc;€“ July 20

# STAT 2507A &acirc;€“ July 20 - STAT2507AJuly20...

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1 STAT 2507A – July 20 Jerry Situ 9.1 Summer 2009

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Review The following results were obtained from two independent surveys on  average commute time to work. What is the difference in the average time from the two samples? If you are told that past research shows that commuting time IS NOT  normally distributed, what would your answer be now? Would you believe that the two samples are from the same population  (same time, same conditions, same survey. ..same everything)? 2 Sample (i) 1 2 n i 100 10000 x ̅ i 25 min 30 min s 2 36 min 1600 min
Review You are surveying students to see if  they support the university’s policy on  not accepting credit cards for tuition.  Assuming you will do a simple random  sample of the university’s policy, what  sample size would you need to ensure  that your estimate on the proportion of  students is accurate within 2  percentage points at a confidence level  of 95%? 3

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Hypothesis testing What is it? It is a procedure to test whether a  hypotheses is supported or not by the  evidence. It tests a hypothesized value of a  parameter. How does it differ from estimation? Estimation: attempt to find the true value Hypothesis testing: validate or not the  hypothesis 4
Hypothesis testing (2) What are we testing? A “null hypothesis” (H

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STAT 2507A &acirc;€“ July 20 - STAT2507AJuly20...

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