BUS310_L16_3.10.11 - Inferential Statistics Hypothesis...

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Lecture 16: Inferential Statistics / Hypothesis Testing II PS4 (focus: Chapter 8) Chapter 9 Chapter 10 PS5 (Chapters 9 and 10)
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PS4
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Problem Set 4 (Chapter 8: Confidence Intervals) 4. (2 points) This problem is based on the file ‘BANKCOST1.xls’. The data represents a sample of 23 banks and gives you two numerical variables: Minimum deposit to open Bounced-check fee Construct 95% Confidence intervals for the population mean for each of these two variables and write a one sentence interpretation for each of the 2 intervals you obtained. Also for each interval assess whether the assumption that the data comes from a Normally distributed population is acceptable for each of the 2 sets of data (with Skewness and Kurtosis, and Normal Probability Plot)
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a) Confidence Interval Estimation with PHStat ‘Confidence Intervals’ The mean minimum deposit to open an account for all banks is estimated as $56.52 based on the sample. We can be 95% confident that the population mean falls between $31.51 and $81.53 (If the assumption of normality is confirmed) BANKCOST1.xls PHStat, ‘Confidence Intervals’, ‘Estimate for the Mean, sigma unknown’
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Assumptions (What do you need to know to make this estimate valid?) Sample size is large (n>30) Data is normal Check Skewness and Kurtosis for normality: à Distribution is NOT normal à Assumption is NOT valid In this case, the t-test is not valid. We cannot use this BANKCOST1.xls
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Normal Probability Plot to evaluate the assumption BANKCOST1.xls Normal Probability Plot: ‘PHStat’, ‘Probability & Prob. Distributions’, ‘Normal Probability Plot’
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Boxplot or Normal Probability Plot to evaluate the assumption Boxplot: ‘PHStat’, ‘Descriptive Statistics’, ‘Boxplot’ BANKCOST1.xls
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a) Confidence Interval Estimation with PHStat ‘Confidence Intervals’ The mean bounced check fee for all banks is estimated as $23 based on the sample. We can be 95% confident that the population mean falls between $21.01 and $24.99 (if the assumptions are met and the t-test is valid) BANKCOST1.xls PHStat, ‘Confidence Intervals’, ‘Estimate for the Mean, sigma unknown’
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B) Assumptions (What do you need to know to make this estimate valid?) Sample size is large (n>30) Data is normal Check Skewness and Kurtosis for normality: à Distribution is approximately normal à Assumption is valid Also use BANKCOST1.xls
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c) Normal Probability Plot to evaluate the assumption. Normal Probability Plot: ‘PHStat’, ‘Probability & Prob. Distributions’ , ‘Normal Probability Plot’ BANKCOST1.xls
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Boxplot or Normal Probability Plot to evaluate the assumption Boxplot: ‘PHStat’, ‘Descriptive Statistics’, ‘Boxplot’ BANKCOST1.xls
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Problem Set 4 (Chapter 8: Confidence Intervals) 5. (2 points) Problem 8.26 In a survey, 27% of small business owners indicated that they never check in with the office when on vacation. The article did not disclose the sample size used in the study. a)
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This note was uploaded on 04/07/2011 for the course BUS 311 taught by Professor Reardon,j during the Spring '08 term at University of Hawaii, Manoa.

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BUS310_L16_3.10.11 - Inferential Statistics Hypothesis...

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