top image
home  /  pages  /  tech tips  /  contact about

Rostering and scheduling assistant

Problem: Many rostering or scheduling problems can be phrased as the distribution of points or units among a group of people over a certain time period. One point could represent one day of work; working on a weekend or a holiday could be worth two points. If subsets of people in the group work part-time, though, the math gets a little confusing.

Example: over a period of 2 months, divide 120 points over a group of 20 people, 15 of which work full time (100% or 1.0), 3 of which work four days per week (80% or 0.8), and 2 of which work 3 days per week (60% or 0.6). How many points worth should each person work?

Solution #1: chicken out, use the form below.

Solution #2, do it by hand: First calculate the "group value" for each group, where "group value" is the number of people multiplied by the percentage they work. For example, the first group contains 15 people that work 100% (or 1.0). Multiply: 15 * 1.0 = 15 is the group value. The second group contains 3 people that work 80% (or 0.8). Multiply: 3 * 0.8 = 2.4 is the group value. The third group contains 2 people that work 60% (or 0.6). Multiply: 2 * 0.6 = 1.2 is the group value. Now add up all the group values: 15 + 2.4 + 1.2 = 18.6. Now divide the total number of points (120) by the sum of the group values (18.6). Divide: 120/18.6 = 6.4516. Now multiply that number by each group value that we calculated before. For the first group, the group value was 15, so the first group needs to work a total of 6.4516 * 15 = 96.77 points; since there are 15 people in the group, that's 96.77 / 15 = 6.4516 units per person. For the second group, the group value was 2.4, so the second groups needs to work a total of 6.4516 * 2.4 = 15.48 points; since there are 3 people in the group, that's 15.48 / 3 = 5.16 points per person. For the last group, the group value was 1.2, so the last group needs to work a total of 6.4516 * 1.2 = 7.74 points; since there are 2 people in the group, that's 7.74 / 2 = 3.87 points per person.

So, you're a chicken: the easy solution

Note that not all rows in this form need to be filled out. If there are only 3 groups (as in the example above), then specify the numbers only for group 1, group 2, and group 3 and leave the rest zero.

Beware: the fields in this form are not verified. If you make a mistake and you get an error, then verify your numbers. The form won't do it for you.

If there is a problem (or you want to say thank-you), please contact me.

# of points to divide
# people in group 1  percent this group works (range 1-100)
# people in group 2  percent this group works (range 1-100)
# people in group 3  percent this group works (range 1-100)
# people in group 4  percent this group works (range 1-100)
# people in group 5  percent this group works (range 1-100)
# people in group 6  percent this group works (range 1-100)
# people in group 7  percent this group works (range 1-100)
# people in group 8  percent this group works (range 1-100)
# people in group 9  percent this group works (range 1-100)
# people in group 10  percent this group works (range 1-100)
URL: http://thomer.com/roster/index.html
Copyright © 1994-2011 by Thomer M. Gil
Updated: 2010/12/10