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Business Statistics
1. What is sampling distribution? An automobile manufacturer claims that a particular model gets 28 KM per liter of petrol, but the Environmental Protection Agency, using a sample of 50 automobiles of this model, finds the sample mean to be 26.8 km/ltr. From previous studies, the population standard deviation is known to be 5 km/ltr. Could we reasonably expect (within 2 standard errors) that we could select such a sample if indeed the population mean is 28 km/ltr? Justify. (10 Marks)
2. Raj studios a Tollywood casting company, is selecting a group of extras for a movie. The ages of the first 30 men to be interviewed are.
50 56 55
54 55 61
49 52 57
60 51 59
56 57 56
62 52 54
55 49 52
61 60 51
57 56 59
52 54 49
The director of the movie wants men whose ages are grouped around 50 years. The director suggests that a standard deviation of 3 years would be acceptable. Does this group of extras qualify to the director’s requirement? (10 Marks)
3. Historically, diesel has mostly been cheaper than petrol in South Africa, though this has not always been the case, and not a trend seen around the world. One of the key differences in the pricing of diesel versus petrol, is that diesel prices reflect wholesale prices, not the price you would pay at the pumps. For example, the wholesale inland diesel price for August was at R10.96 at the beginning of the month, while Caltex’s retail version – Caltex 50 diesel with Techron – sells at R11.33 per litre. Over the past decade, both the petrol and diesel prices have seen some significant fluctuations, but petrol (95 grade) has seen the biggest overall increase, having jumped 75.4% since 2006.
Year Petrol-Unleaded 93 Petrol-Unleaded 95 Diesel 0.05%
2006
R6.92
R7.04
R6.54
2007
R6.88
R7.01
R6.51
2008
R10.20
R10.40
R11.27
2009
R7.52
R7.69
R6.65
2010
R8.02
R8.17
R7.38
2011
R9.91
R10.09
R9.30
2012
R10.83
R11.04
R10.25
2013
R13.32
R13.55
R12.48
2014
R14.08
R14.33
R12.84
2015
R13.01
R13.26
R10.94
2016
R12.08
R12.35
R10.96
Source: Department of Energy; Inland prices, August The fuel price is affected by two major components: the global oil price, and the currency exchange rate between the rand and the dollar. Between 2014 and 2016, fuel prices (both diesel and petrol) have shown a year-on-year decline, boosted by a much lower global oil price, which has dropped below $50 a barrel, with little hope that it will balloon past that level in the near future. However, much of the benefit delivered by lower oil prices has been undone by weakness in the rand – brought about by a struggling economy, poor growth policies and a number of political scandals involving president Jacob Zuma.
a. Explore the trend in the petrol price (for both unleaded 93 and unleaded 95) using regression trend analysis. Using the data, forecast the petrol price for 2017, 2018 and 2019.
b. Explore the trend in the diesel price using regression trend analysis. Using the data, forecast the diesel price for 2017, 2018 and 2019. Out of the three regression models, which model is the strongest in predicting the fuel price?
Assignment Solutions, Case study Answer sheets
Project Report and Thesis contact
aravind.banakar@gmail.com
www.mbacasestudyanswers.com
ARAVIND – 09901366442 – 09902787224
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