learning curves. the learning curve graphic illustration of the productivity change as a function of...

Learning curves

The learning curve

• Graphic illustration of the productivity change as a function of repetition (or time). It is relatively stable in time, thus we can use it to predictions.

• Theodore Paul Wright (1936)

Learning curve with no change in the task

On a log-log graph

Idő

Learning curve with innovations

Based on empirical findings

• Decrease (%) in time needed is constant for every duplication of the number of repetitions. It is typicaly between 10-20%.

Example

• Learning percentage: 80%• First performance time: 10 hrs• How much time it needs to finish the 2nd, 4th,

8th and 16th repetition? – 2nd: 10*0,8 = 8– 4th: 8*0,8 = 6,4– 8th: 6,4*0,8 = 5,12– 16th: 5,12*0,8 = 4,1

General formula

1) For the nth unit:Tn = T1 * nb

b = learning percentage) / ln2For the 3rd and 4th unit:T3 = 10*3(ln0.8/ln2) = 7,02

T4 = 10*4(ln0.8/ln2) = 6,40

2) From table: Tn = T1 * coefficient

Example 2• We want to produce 20 units. Learning percentage is 80. T1

= 400 hrs. a) How much is the production time for the 20th unit? b) What will be the cumulative production time? What is the

average production time?

• T20 = 400*20(ln0.8/ln2) = 152.48

• T20 = 400*10.485 = 4194

• 4194/20 = 209.7

Mass production and learning curves

Evaluating employees