In: Statistics and Probability
What is the 95 percent confidence intervals for the average daily inventory holding cost Pre- and Post- COVID-19 (X_1&〖 X〗_2 )? And what do you conclude by comparing these intervals? Also what is the 99 percent confidence interval for the average daily inventory holding cost Post- COVID-19 (X_2 )? And what do you conclude by comparing the 95 and 99 percent confidence intervals for the average daily inventory holding cost Post- COVID-19 (X_2 )?
Date | 1/Nov/2019 | 2/Nov/2019 | 3/Nov/2019 | 4/Nov/2019 | 5/Nov/2019 | |
Pre-COVID-19 | Y1 | 4614.6 | 4615.0 | 4614.6 | 4614.9 | 4616.1 |
X1 | 8.4 | 8.1 | 9.2 | 8.4 | 6.1 | |
Date | 1/Apr/2020 | 2/Apr/2020 | 3/Apr/2020 | 4/Apr/2020 | 5/Apr/2020 | |
Post-COVID-19 | Y2 | 2938.2 | 2942.9 | 2937.9 | 2941.2 | 2934.4 |
X2 | 11.7 | 8.0 | 10.2 | 9.3 | 11.3 |
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.