BUS310_L16_3.10.11

# 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)
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)
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
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
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
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
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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