The equality of Air Canada flight times (in hours) between Vancouver and San Francisco is tested using Excel. A preliminary F test shows that there is no significant difference between the two sample variances, so, as shown in the accompanying figure (a = 0.05), the t test assuming equal variances was used.
a. Based on the displayed results below, construct a 95% confidence interval for the difference μ1 - μ2 where μ1 denotes the mean flight time from Vancouver to San Francisco. Do the confidence intervals contain 0? What can you conclude about equality of the mean flight times in both directions?
b. Use elements from the Excel display on the next page to answer these questions: At the 0.05 significance level, test the claim that flights from Vancouver to San Francisco take a longer time than flights in the other direction. What is the test statistic? What is the critical value? What is the P-value?

Transcribed Image Text:

San Francisco to Vancouver Vancouver to San Francisco 2.30 2.20 1.97 2.22 2.12 1.95 2.03 2.30 2.15 2.33 2.15 Based on data from Gary Murphy, chief flight dispatcher, Air Canada. 1.80 1.68 2.03 1.83 1.77 1.98 1.85 X Microsoft Excel- ttest two small samples lor means- equal ㅣ *) Ele Edt yes, Insert Format lois Data wndow telp Aria A20 1t-Test Two-Sample Assuming Equal Variances Veniable 1 Variable 2 21560606 0 0173485 00148148 一 195 4 Mean 5 Variance 6 Observations 7 Pooled Variance B Hypothesized Mean Difference 0 0163984 df 10 t Stat 1 PTt) one-tail 12 t Critical one-tail 3 PTt) two-tail 14 t Critical two-tail 16 4 943293 7.338E-05 1.7453842 0.0001468 21199048