Skodel Ltd employs a local transport company to deliver beers to local supermarkets. To develop better work schedules, the managers want to estimate the total daily travel time for their drivers’ journeys. Initially, the managers believed that the total daily travel time would be related closely to the number of miles travelled in making the daily deliveries (Table 8.23).

(a) Plot a scatter plot and comment on a possible relationship between travel time and miles travelled.

(b) Use the Excel data analysis regression tool to undertake the following tasks:

(i) State the least squares regression model equation

(ii) Comment on model reliability (r and COD)

(iii) Is the independent variable significant (F or t-test)?

(iv) Check model assumptions (residual and normality checks).

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Journey 1 2 3 4 5 a 7 8 00 9 10 Table 8.23 Miles travelled, x 100 50 100 100 50 80 75 65 90 90 Travel time (hours), y 9.3 4.8 8.9 6.5 4.2 6.2 7.4 6.0 7.6 6.1 Journey 11 12 13 14 15 16 17 18 19 20 Miles travelled, x 85 62 98 58 73 81 66 72 53 56 Travel time (hours), y 7.4 6.4 8.4 4.9 6.8 7.8 6969 6.2 7.3 4.4 4.6