Lecture 13

# Lecture 13 - a mean gas mileage of 26 mpg. ( = 1.5) A...

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Hypothesis Testing Procedure for Hypothesis Testing: (1)State Hypotheses (about Population Parameter) Null Hypothesis – The hypothesis you assume is true; (Ex. µ = 26) Alternative (or Research) Hypothesis what you suspect is true. 3 choices µ < 26, µ > 26, µ ≠ 26 (2)Check Assumptions (Conditions required) f8e5Χ is approximately normal by CLT 1

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(3) Calculate Test Statistic and p-value z = ( f8e5Χ - µ 0 ) σ/√n p-value: the probability of the of the test statistic in the direction of the Alternative Hypothesis (4)Compare p-value to significance level Significance level is α. If p-value is less than α, reject H 0 . *if no α is given then assume α=0.05 (5)State Conclusion Does test support H A ? 2
Example 1 . A car manufacturer advertises

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Unformatted text preview: a mean gas mileage of 26 mpg. ( = 1.5) A consumer group suspects that it is less. A sample of 33 cars had an average of 25.2 mpg. Statistical Reasoning: Assume that the true mean is 26 mpg. Is it just by chance that the sample average is less, or does this indicate that the true mean is less? If the true mean is 26 mpg, how likely is it that 33 cars would have an average of 25.2 mpg or less? 3 4 Example 2. A company produces a 454 g bag of pretzels. ( = 3.9) To check the filling process, 50 bags are selected and weighed. The average weight was 455 g. Is there evidence to indicate that the bags are not filling properly? 5 6 7 8 9 10 11 12 13...
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## This note was uploaded on 02/15/2009 for the course STAT 2004 taught by Professor Melutz during the Fall '07 term at Virginia Tech.

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Lecture 13 - a mean gas mileage of 26 mpg. ( = 1.5) A...

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