A sample of data on daily prices of three petrol stations over a two week period have been collected in the table below. The total sample size should be 42 (3 stations x 14 observations per station).
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Observations of daily price of standard unleaded fuel
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Biogas Bellowrie
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Caltex/WoolworthsKenmore
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Coles Express Chapel Hill
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Fri 14/09/2012
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137.4
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139.2
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141.4
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Sat 15/09/2012
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141.6
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143.9
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145.9
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Sun 16/09/2012
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146.5
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147.9
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150.5
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Mon 17/09/2012
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148.4
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149.9
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152.4
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Tues 18/09/2012
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148.1
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149.5
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151.9
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Wed 19/09/2012
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147.3
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148.6
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150.9
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Thurs 20/09/2012
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146.2
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147.5
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149.4
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Fri 21/09/2012
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145.3
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146.5
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148.5
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Sat 22/09/2012
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144.5
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145.7
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147.8
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Sun 23/09/2012
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143.9
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145.1
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147.1
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Mon 24/09/2012
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142.6
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143.8
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145.8
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Tues 25/09/2012
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141.2
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142.4
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144.4
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Wed 26/09/2012
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139.7
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140.9
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142.9
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Thurs 27/09/2012
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139.7
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139.9
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141.9
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The lecturer is looking for us to analyse the cycle of petrol pricing, what days it reaches its peak and low and how long the cycle is.
(a) Calculate the mean, mode and median of the ungrouped data for each station separately and for the combined sample. So this means to calculate the mean, mode and median of ungrouped data for each column (station) and for all columns (all stations) using AVERAGE(:), MODE (:) and MEDIAN (:). Present the results of the calculation. Include in excel table to be copied and pasted in word document.
(b) For the combined sample, prepare a frequency distribution table (in excel) and plot its frequency histogram. Explain your choice of number of classes and class intervals. (Hint... should be 6 classes). Both the frequency distribution table and the histogram should be separate excel workings to be copied and pasted into word doc, ie histogram will be in excel format but able to be copied and pasted.
(c) Calculate the mean, mode and median of the grouped data derived from the frequency distribution above. Compare the results obtained from (a) and (c).
(d) Discuss any patterns or movements of petrol prices that emerge from results.