Business Decision Making

Task 1:

Percentiles: the pth percentile is a number such that p% of the observations of the data set fall below and (100-p)% of the observation fall above it

Quartiles: divide the data set into four parts, each contains the same number of observations

Q1- the first quartile: the value of the observation of which 25% of observations fall below

Q2 - the second quartile: the median (50% of the observations fall below)

Q3 - the third quartile: the value of the observation of which 75% of observations fall below

Calculation:

35.452 \ 40.981 \ 41.469 \ 42.777 \ 43.491 \ 57.669 \ 59.476 \ 63.103 \ 67.990 \ 68.542 \ 69.574 \ 73.457 \ 76.908 \ 84.457 \ 85.891 \ 89.124

n = 16

Location of Q1: [pic]

Location of Q2: [pic]

Location of Q3: [pic]

Location of Q4: [pic]= 12.75

Then: Q1 = 41.469 + 0.4(42.777 – 41.469) = 41.9922

Q2 = 42.777 + 0.25(43.491 – 42.777) = 42.9555

Q3 = 69.574 + 0.05(73.457 – 69.574) = 69.76815

Q4 = 73.457 + 0.75(76.908 – 73.457) = 76.04525

Inter-quartile range:

IQR = Q3 – Q1 =69.76815– 41.9922= 27.77595

From 2008 to 2011, the oil price is continues increasing and the sale are decreasing. The more the oil price is increase, the more the sales is decrease. About task 1, we use formula Q= percentile.(n+1) to calculate the value of quartiles in 4 years. Then we deduce the position of quartiles through that value. The value of quartiles depends on the percentiles that are given

The oil price affect price and yield of spare parts for automobiles. In addition, the sale increase over time. Although, the original sales is low but after a few years, company has a large amount of revenues. Because, they gradually gain the trust of customers. That helps the salepriceare less dependent to oil price. When the oil price increases, sales reduce; while oil prices reduce, the sales increase.

Task 2:

2.1 Choose and perform appropriate method(s) to...