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Question 2 The unit coordinator of a statistics course is looking to predict how long it will take to mark a round of assignments. The course consists of both u dergraduate and postgraduate mathematics students. Each cohort requires different assessment items and thus a different amounts of time to mark An undergraduate assignment takes an average of 5 minutes to mark with a standard deviation of 2 minutes. A postgraduate assignment can be slightly harder to predict However, the unit coordinator plans to fit the time to mark a post graduate assignment to the pdf given by 1.1 0, otherwise a Write an equation for the time it would take to mark a class of n under graduates and n postgraduates b Calculate the expected time to mark the class. c Calculate the variance of the time to mark the class. For question 2a We are told each individual assignment has a specific mean and standard deviation or pdf. This implies that each assignment is it's own random variable (RV). You need to create a model for calculating how long it takes to mark a class of size n1+n2 students using these RVs. with these. Consider a line of four undergrad students: (X1, X2, X3, X4). (that is n1=4, n2=0) Each student comes up to me and hands me their assignment to mark. Student 1 takes 5 minutes to mark Student 2 takes 4 minutes to mark Student 3 takes 4.5 minutes to mark Student 4 takes 5 minutes to mark. At the end, I calculate the time to mark the class by adding together each individual assignment (C-18.5 minutes) If I had a different 4 students, I would take a different amount of time to mark, but would calculate it in the exact same way. So the time to mark a class is a new RV made up of the individual assignment RVs

Answer 1

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