BUS105 Group-based Assignment

This assignment is worth 20% of the final mark for BUS105 Statistics.

The cut-off date for this assignment is 30 September 2026, 2355hrs.

Background

As part of the region’s sustainability initiatives, several public transport operators in ASEAN countries have begun piloting electric buses to reduce carbon emissions and noise pollution. One operational concern is battery degradation, as reduced battery health can shorten driving range, increase charging frequency, and raise long-term maintenance costs.

GreenMove Transport Pte Ltd operates a mixed fleet of electric buses supplied by two manufacturers: Supplier A and Supplier B. Both suppliers claim that their batteries perform similarly under ASEAN’s hot and humid climate. However, the engineering team suspects that Supplier A’s batteries may degrade faster over time.

Assume that you are working as a Data Analyst Intern in GreenMove’s Analytics Unit. During a six-month pilot programme, engineers recorded the percentage loss in battery capacity for buses from each supplier after the buses had operated for the same distance.

Battery capacity loss is measured as a continuous variable (in percentage points), calculated by comparing current maximum charge capacity to the original factory-rated capacity. The recorded battery capacity loss data are provided in the Excel file Battery Degradation.xlsx.

Question 1

(a) Please limit your answer (including tables and graphs, if any) for Part (a) to one (1)

(i) Determine the 90% confidence intervals for the mean battery capacity loss for Supplier A and Supplier B, respectively.

(ii) Interpret the meaning of the constructed 90% confidence intervals in this context.

(iii) Based on the two constructed intervals in (i), briefly discuss whether you can conclude that the mean battery capacity losses for the two suppliers are different.

(30 marks)

(b) Please limit your answer (including tables and graphs, if any) for Part (b) to two (2)

(i) Execute an appropriate hypothesis test at the 0.1 significance level to evaluate the engineering team’s claim. State the assumption(s) of your test. You are not required to verify them.

(ii) Illustrate the hypothesis test performed in (i) using a graph, with an appropriate distribution curve. Manual drawing is acceptable, provided that the key properties of the distribution are correctly represented.

(35 marks)

Question 2

After reviewing the analysis results obtained in Question 1, the Head of GreenMove’s Analytics Unit, Ms. Tan, has asked you to:

• Explain the conceptual differences between the confidence interval analysis in Question 1(a) and the hypothesis testing analysis in Question 1(b)
• Recommend which approach is more appropriate for addressing the engineering team’s concern with two (2)

Write an email to address her questions. You are not required to restate or interpret the analysis results obtained in Question 1 in the email.

Your email should be less than 350 words. Please indicate the word count at the end of your answer.

(35 marks)

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