Activity A Activity B Optimistic time ($t_o$) = 4 days Optimistic time ($t_o$) = 4 days Most likely time ($t_l$) = 7 days Most likely time ($t_l$) = 6 days Pessimistic time ($t_p$) = 16 days Pessimistic time ($t_p$) = 22 days
PERT Standard Deviation Calculation
The standard deviation for project activities is calculated using the PERT (Program Evaluation and Review Technique) formula, which estimates the dispersion of activity durations.
The formula for standard deviation ($\sigma$) is:
$ \sigma = \frac{t_p - t_o}{6} $
Where:
- $t_p$ = Pessimistic time estimate
- $t_o$ = Optimistic time estimate
Activity A Standard Deviation
Given values for Activity A:
- Optimistic time ($t_o$) = 4 days
- Pessimistic time ($t_p$) = 16 days
Calculation:
$ \sigma_A = \frac{16 \text{ days} - 4 \text{ days}}{6} = \frac{12 \text{ days}}{6} = 2 \text{ days} $
Activity B Standard Deviation
Given values for Activity B:
- Optimistic time ($t_o$) = 4 days
- Pessimistic time ($t_p$) = 22 days
Calculation:
$ \sigma_B = \frac{22 \text{ days} - 4 \text{ days}}{6} = \frac{18 \text{ days}}{6} = 3 \text{ days} $
Conclusion
The standard deviation for Activity A is 2 days, and the standard deviation for Activity B is 3 days.
Important Questions from Basics of Probability
If the data are skewed, which option of central tendency measure is the most unreliable indicator?
In a negatively skewed distribution
If the distribution is negatively skewed, then the:
The first four moments about the mean of distribution are 0, μ 2, 0.7 and 18.75. If the distribution is mesokurtic, the value of μ 2, is
If Mean > Median > Mode, the distribution is:
