The Airports Company of South Africa (ACSA) is investigating the length of flight delays on departure. It is acceptable to have flight delays due to various environmental and operational factors, provided these delays do not exceed 10 minutes, on average. ACSA management would conduct an investigation into the causes of lengthy flight delays if the average delay significantly exceeds 10 minutes. To test whether flight delays do not exceed 10 minutes on average, a random sample of 80 delayed flights over the past month were drawn from airport records.
(a) Use the Histogram option in Data Analysis to check the assumption of normality. Comment on the findings.
(b) What recommendation would you make to ACSA management about the average length of flight delays? Should they conduct a detailed investigation into the causes of flight delays? Base your recommendation on the results of a hypothesis test for a single mean conducted at a 10% level of significance. Show the null and alternative hypothesis for this management question.