# Seminar2_Tutor_Copy_SUSS-6.pdf - 11-Aug-19 BUS105...

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11-Aug-19 1 BUS105: Statistics Seminar 2 - Unit 2 -Confidence Interval -Hypothesis Testing -Analysis of Variance Activity 2.1 Confidence Interval Rozex Hotel has been sending its staff for customer service training for the last two years. Recently, Rozex has conducted a round of mystery guest survey to monitor the progress. The survey scores is enclosed (see Activity2.1_Data.xls). The industry average score for the customer satisfaction is 80 (out of a scale of 100).
11-Aug-19 2 Activity 2.1 In group of 4, 1. Use Excel to construct the 90% confidence interval for the mean customer service scores. 2. Using answer in part 1, do you think there is sufficient evidence to conclude that Rozex Hotel customer service has met the industry standard? You may refer to “Excel Self Practice Prior Seminar 2” Practice 2.1. Activity 2.1 Debrief Confidence Interval Estimates for μ Use Z -distribution If the population standard deviation is known . Use t -distribution If the population standard deviation is unknown . Note: 1. For the use of Z -distribution, we require that X is normal or use a large sample size to overcome this. 2. For the use of t -distribution, we require X to be normal or nearly normal. n Z X 2 / n s t X n 1 , 2 /
11-Aug-19 3 Activity 2.1 Answer Based on Excel Output, the 90% confidence interval is (65.55, 73.39). This interval is below 80 and did not contain 80. Therefore, the customer service level of Rozex Hotel is still below the industry norm despite the training initiatives. Score Mean 69.46538 Confidence Level(90.0%) 3.922194 Lowe Limit = 69.47 3.92 = 65.55 Upper Limit = 69.47 3.92 = 73.39