In: Operations Management
Discuss the appropriate statistical technique that can explain the variation in the daily sales because of the daily inventory holding cost Post-COVID-19 post COVID 19. Justify your answer.
Answer a :
Date | Pre-COVID-19 | Date | Post-COVID-19 | ||
Y1 | X1 | Y2 | X2 | ||
01-Nov-19 | 4365.5 | 7 | 01-Apr-20 | 3612.2 | 11.9 |
02-Nov-19 | 4365.8 | 7.1 | 02-Apr-20 | 3617 | 8.6 |
03-Nov-19 | 4366.3 | 7.2 | 03-Apr-20 | 3614.9 | 7.9 |
04-Nov-19 | 4365.9 | 7.7 | 04-Apr-20 | 3612.3 | 11.4 |
05-Nov-19 | 4365.7 | 7.3 | 05-Apr-20 | 3617.5 | 8.1 |
Average | 7.26 | 9.58 |
The average daily inventory holding cost during Pre- COVID-19 is 7.26
The average daily inventory holding cost during Post- COVID-19 is 9.58.
Parameter: Mathematically summarization and description of collections of population data.
Statistic: Mathematically summarization and description of collections of sample data.
These means are the sample statistics because the data is for only 5 days each.
Answer b :
95% Confidence interval for X1
Sample mean of X1 is
Sample standard deviation of X1 is
Degree of freedom = 5-1 = 4
From t-table, for 95% confidence value and degree of freedom =4,
t = 2.776
The 95% Confidence interval is calculated as:
The 95% confidence interval for average daily inventory holding cost Pre- Covid-19 is (6.60, 9.48)
95% Confidence interval for X2
Sample mean of X2 is
Sample standard deviation of X1 is
Degree of freedom = 5-1 = 4
From t-table, for 95% confidence value and degree of freedom =4,
t = 2.776
The 95% Confidence interval is calculated as:
The 95% confidence interval for average daily inventory holding cost Post- Covid-19 is (8.23, 11.97)
Comparing the 95% confidence interval for average daily inventory holding cost for Pre and Post- Covid-19, we see that there is a small overlap in the confidence interval regions of both values. Thus there isn't convincing evidence that average inventory cost for Pre and Post Covid-19 are different.
99 percent confidence interval for tX2
Degree of freedom = 5-1 = 4
From t-table, for 99% confidence value and degree of freedom =4,
t = 4.602
The 99% Confidence interval is calculated as:
The 99% confidence interval for average daily inventory holding cost Post- Covid-19 is (7.00, 14.01)
The 95% confidence interval for X2 is (8.23, 11.97), while the 99% confidence interval is (7.00, 14.01). We can be 95% confidence that the average daily inventory holding cost Post- Covid-19 lies between 8.23 and 11.97 while we can be 99% confidence that the average daily inventory holding cost Post- Covid-19 lies between 7.00 and 14.01.
Comparing both the confidence intervals we conclude that, the 99% confidence interval is significantly wider than the 95% confidence interval.
Answer c :
For computation of mean and sample standard deviation, S of X1 in excel follow the given steps:
Answer d :
The data set
Pre-COVID-19 | Post-COVID-19 | |||||
Date | Sales (Y1) | Inventory (X1) | Date | Sales (Y1) | Inventory (X1) | |
01 November 2019 | 3226.7 | 8.5 | 01 April 2020 | 1714.4 | 13.1 | |
02 November 2019 | 3224.4 | 8.2 | 02 April 2020 | 1720.3 | 9.8 | |
03 November 2019 | 3228.1 | 7.3 | 03 April 2020 | 1710.7 | 13.6 | |
04 November 2019 | 3226.2 | 8 | 04 April 2020 | 1711.1 | 14.3 | |
05 November 2019 | 3226.6 | 8 | 05 April 2020 | 1709.6 | 14.3 | |
06 November 2019 | 3226.7 | 7.9 | 06 April 2020 | 1710.3 | 14.7 | |
07 November 2019 | 3226.8 | 7.6 | 07 April 2020 | 1702.6 | 17.8 | |
08 November 2019 | 3223.7 | 8.4 | 08 April 2020 | 1718.4 | 11.1 | |
09 November 2019 | 3225 | 8.4 | 09 April 2020 | 1712.3 | 10.8 | |
10 November 2019 | 3222.5 | 8.3 | 10 April 2020 | 1713.8 | 11.7 | |
11 November 2019 | 3223.8 | 7.9 | 11 April 2020 | 1718.5 | 7.3 | |
12 November 2019 | 3226.9 | 7.7 | 12 April 2020 | 1717.6 | 11 | |
13 November 2019 | 3224.9 | 8 | 13 April 2020 | 1710.5 | 15.3 | |
14 November 2019 | 3230.1 | 7.8 | 14 April 2020 | 1713.3 | 14 | |
15 November 2019 | 3225.6 | 7.9 | 15 April 2020 | 1713.5 | 11 | |
16 November 2019 | 3225.1 | 7.7 | 16 April 2020 | 1715.1 | 10.9 | |
17 November 2019 | 3225.7 | 7.8 | 17 April 2020 | 1718 | 10.3 | |
18 November 2019 | 3224.4 | 8.4 | 18 April 2020 | 1717.5 | 10.9 | |
19 November 2019 | 3224.9 | 7.8 | 19 April 2020 | 1716.1 | 9.7 | |
20 November 2019 | 3226.3 | 7.7 | 20 April 2020 | 1715.4 | 12.2 | |
21 November 2019 | 3228.1 | 7.4 | 21 April 2020 | 1715.8 | 11.2 | |
22 November 2019 | 3225.7 | 8.1 | 22 April 2020 | 1709 | 13.7 | |
23 November 2019 | 3224.4 | 8.2 | 23 April 2020 | 1710.8 | 13.2 | |
24 November 2019 | 3225.8 | 8.1 | 24 April 2020 | 1714.5 | 10.5 | |
25 November 2019 | 3225.7 | 7.9 | 25 April 2020 | 1714.4 | 12 | |
26 November 2019 | 3227.3 | 8.2 | 26 April 2020 | 1715.4 | 12.7 | |
27 November 2019 | 3226.2 | 7.8 | 27 April 2020 | 1717.9 | 10.2 | |
28 November 2019 | 3225.6 | 8.4 | 28 April 2020 | 1716.2 | 12.3 | |
29 November 2019 | 3226.8 | 7.9 | 29 April 2020 | 1716.5 | 11.6 | |
30 November 2019 | 3224.4 | 8.1 | 30 April 2020 | 1711.6 | 15.3 | |
01 December 2019 | 3228.5 | 7.7 | 01 May 2020 | 1717.5 | 11.8 | |
02 December 2019 | 3227 | 7.9 | 02 May 2020 | 1721.6 | 6.4 | |
03 December 2019 | 3224.5 | 8 | 03 May 2020 | 1713.2 | 12.4 | |
04 December 2019 | 3225 | 8 | 04 May 2020 | 1713.9 | 12.8 | |
05 December 2019 | 3227.7 | 7.9 | 05 May 2020 | 1709.1 | 14.4 | |
06 December 2019 | 3228.6 | 7.8 | 06 May 2020 | 1721.2 | 9.5 | |
07 December 2019 | 3228.4 | 7.5 | 07 May 2020 | 1720.1 | 9.6 | |
08 December 2019 | 3227 | 7.9 | 08 May 2020 | 1713.9 | 9.5 | |
09 December 2019 | 3227 | 8.1 | 09 May 2020 | 1712.7 | 12 | |
10 December 2019 | 3227.6 | 7.6 | 10 May 2020 | 1722.3 | 8.6 | |
11 December 2019 | 3226.8 | 7.6 | 11 May 2020 | 1719.7 | 11.1 | |
12 December 2019 | 3229 | 7.7 | 12 May 2020 | 1713.9 | 14.4 | |
13 December 2019 | 3224 | 7.9 | 13 May 2020 | 1711.8 | 12.8 | |
14 December 2019 | 3223.6 | 8 | 14 May 2020 | 1719 | 8 | |
15 December 2019 | 3228 | 7.6 | 15 May 2020 | 1720.8 | 9.9 | |
16 December 2019 | 3226.1 | 8.1 | 16 May 2020 | 1715.8 | 13.7 | |
17 December 2019 | 3226.5 | 8 | 17 May 2020 | 1717.4 | 8.1 | |
18 December 2019 | 3229.2 | 7.6 | 18 May 2020 | 1716 | 11 | |
19 December 2019 | 3223.5 | 8.7 | 19 May 2020 | 1710.9 | 14.8 | |
20 December 2019 | 3227.3 | 7.8 | 20 May 2020 | 1716.7 | 10.2 | |
21 December 2019 | 3225.5 | 7.8 | 21 May 2020 | 1716.4 | 11 | |
22 December 2019 | 3229.1 | 7.7 | 22 May 2020 | 1715.6 | 11.2 | |
23 December 2019 | 3225.6 | 8.3 | 23 May 2020 | 1716.6 | 12.6 | |
24 December 2019 | 3224.2 | 8.2 | 24 May 2020 | 1714.6 | 11.7 | |
25 December 2019 | 3226.5 | 8.1 | 25 May 2020 | 1719.1 | 10.5 | |
26 December 2019 | 3225.4 | 8.1 | 26 May 2020 | 1716 | 10.1 | |
27 December 2019 | 3224.1 | 8.4 | 27 May 2020 | 1713.4 | 12.9 | |
28 December 2019 | 3227.8 | 7.6 | 28 May 2020 | 1719.2 | 10.7 | |
29 December 2019 | 3226.7 | 7.9 | 29 May 2020 | 1718.5 | 8 | |
30 December 2019 | 3228.5 | 7.6 | 30 May 2020 | 1717.4 | 10.2 | |
31 December 2019 | 3225.4 | 7.8 | 31 May 2020 | 1720.9 | 10.1 |
The analysis
Pre-COVID-19 | Post-COVID-19 | |||
Correlation Co-efficient | Correlation Co-efficient | |||
Sales (Y1) | Sales (Y1) | |||
Inventory (X1) | -0.647017976 | Inventory (X1) | -0.827745401 | |
Covariance | Covariance | |||
Sales (Y1) | Sales (Y1) | |||
Inventory (X1) | -0.302652513 | Inventory (X1) | -6.605834453 |
From the above analysis we can conclude there is an increase in the stock holding compared to sales in post COVID-19 situation compared to pre COVID-19 situation.
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