QTM 2 - Summarising Data - Tutorial Solutions

# QTM 2 - Summarising Data - Tutorial Solutions - QTM Lecture...

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1 QTM Lecture 2 Summarising Data Tutorial Questions & Solutions Q1. The data warehousing team at Tesco’s have given store sales data to a graduate trainee for analysis. The data (in Excel) comprises the following: Number of standard packs of washing powder sold on a typical trading day (Tuesday 3 rd July 2012). Data is available for five brands of washing powder: Daz, Bold, Aerial, Persil and Tesco’s own brand product. Data is available from 300 of Tesco’s stores. Each store is identified by a store code, for example store 5181 is the ‘hyperstore’ in Stockport. A store code starting with a ‘3’ is for a store situated in Scotland, whilst codes starting with a ‘4’ represent Welsh stores and codes starting with a ‘5’ represent English stores. There are also three codes for store size: M is a small/Metro store, S is a superstore and H is a hyperstore. a) Find the mean (average), median and mode sales for Daz washing powder across the three hundred stores (Hint: use an individual formula for each measure). b) Find the mean (average), median and mode sales for the four remaining washing powder brands across the three hundred stores (Hint: copy the formulae from a). c) Find the maximum and minimum sales and standard deviation value for Aerial washing powder across the three hundred stores (Hint: use individual formula for each measure). d) Find the maximum and minimum sales and standard deviation value for the four remaining washing powder brands across the three hundred stores (Hint: copy the formulae from c).

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2 Solutions (a to d) Q2 Using the washing powder data from Q1: a) Use Excel to calculate the summary statistics for the five brands of washing powder. (Hint: increase column widths, reduce decimal places and insert data headings for the summary statistics table to make the data more presentable). b) Daily sales are never higher than 150 packets per day for each brand. Do any of the summary statistics look strange? (Hint: check the minimum and maximum values). c) Sort each column of data and get rid of any data points that are not between 0 and 150. d) Use Excel to calculate the summary statistics for the five brands of washing powder, using the data you ‘cleaned’ in c) e) Check the minimum and maximum values in your new table, are they all between 0 and 150? f) Compare the five means of the ‘clean’ and ‘unclean’ data. What are the main differences? g) Compare the median, modes and standard deviations of the ‘clean’ and ‘unclean’ data. What, if any, are the differences? h) What is the coefficient of variation across the stores for the five brands of washing powder? (Hint: use the ‘clean’ data) Daz Bold Aerial Persil Tesco's Own Mean 39.1 36.3 73.7 68.7 25.5 Median 35 34 52 56 24 Mode 37 54 60 54 25 Minimum 18 -20 29 36 11 Maximum 400 88 5100 1100 59 Standard Deviation 25.1 14.5 291.8 71.0 9.8
3 Solutions a) b) Yes. The maximum packets of washing powder sold for Daz, Aerial and Persil are all much higher than 150. Also, the minimum amount sold for Bold is a minus number.

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