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Learning curve: when is the new person up to speed?

How many times should the new person do the job before she's down to standard time?

Answer: When a new employee learns a task, it goes faster each time. The learning curve says that each time the number of repetitions doubles, time falls to a fixed percentage of the previous time: the learning rate. At 85 % the 2nd time takes 85 % of the 1st time, 4th time 85 % of the 2nd time, and so on. The calculator shows the time at a given repetition, how many times it takes to reach the standard time an experienced user, and total training time. Measure the first time yourself and preferably a couple of repetitions too so you can see your own learning rate.

Formula

Tid ved gentagelse n: Tₙ = T₁ × n^b, hvor b = log(læringsrate) ÷ log(2)

Ved 85 % er b ≈ −0,234: hver fordobling af antallet giver 85 % af den tidligere tid

Gentagelser for at nå normtiden: n = (normtid ÷ T₁)^(1/b), rundet op

Samlet tid for gentagelse 1 til n ≈ T₁ × ((n + ½)^(b+1) − (½)^(b+1)) ÷ (b + 1) (en god tilnærmelse til summen)

Symbols and units in the formula
SymbolMeaningUnit
foerste_tidTime first occasionmin
laeringsrateLearning rate (time at doubling as % of before)%
nRepetition you want to see time forgange
maal_tidStandard time for experiencedmin
=Time at this repetitionmin
=Repetitions to reach standard timegange
=Total time for all repetitions up to and including this (approx.)timer
=Time saved per occasion compared to the first timemin

Validity and source

Source
Learning curve (T.P. Wright 1936) unit-time model

Does not apply when

  • Learning rate is not a constant for a trade. It depends on the task and how well training is arranged. Pure manual, repetitive tasks are often higher than tasks with much thinking but use your own measurements. The curve flattens towards a floor time which the model doesn't itself know.

Worked example

The calculator's own default values inserted. The figures are calculated with exactly the formula the tool uses.

Substituted

  • Time first occasion60 min
  • Learning rate (time at doubling as % of before)85 %
  • Repetition you want to see time for20 gange
  • Standard time for experienced30 min

Giver

  • Time at this repetition29.7 min
  • Repetitions to reach standard time20 gange
  • Total time for all repetitions up to and including this (approx.)12.4 timer
  • Time saved per occasion compared to the first time30.3 min

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Sådan bruger du den

Når en ny medarbejder starter, spørger lederen: hvornår er hun oppe i tempo? Læringskurven giver et svar, du kan planlægge efter, og viser hvor mange timer oplæringen kræver. Den bruges i oplæringsplaner og når en ny metode skal indføres.

Step by step

  1. Mål tiden første gang, opgaven udføres efter instruktion.
  2. Vælg en læringsrate. Mål gerne 2. og 4. gang: forholdet mellem dem er læringsraten.
  3. Sæt normtiden for en erfaren medarbejder.
  4. Læs antal gentagelser for at nå normtiden og den samlede tid.
  5. Følg op med målinger undervejs.

Typical errors

  • At sætte læringsraten uden at måle. Mål 2. og 4. gang.
  • At forvente, at kurven fortsætter nedad for evigt. Den flader ud.
  • At sammenligne folk med hinanden ud fra første gangs tid.
  • At glemme, at lange pauser mellem gentagelserne sætter læringen tilbage.

Examples from everyday life

Ny medarbejder på en maskine

En ny operatør bruger 60 minutter første gang på en omstilling. Erfarne bruger 30 minutter. Du regner med en læringsrate på 85 %.

Time first occasion
60 min
Learning rate (time at doubling as % of before)
85 %
Repetition you want to see time for
20 times
Standard time for experienced
30 min

It means: Ved 20. gang tager omstillingen 29.7 min. Der skal 20 times til at nå normtiden, og de første 20 gange koster 12.4 hours i alt.

Plukning på et lager

En ny plukker bruger 12 minutter på første ordre. Erfarne bruger 6, og læringsraten er 90 %.

Time first occasion
12 min
Learning rate (time at doubling as % of before)
90 %
Repetition you want to see time for
50 times
Standard time for experienced
6 min

It means: Efter 50 ordrer tager en ordre 6.6 min. Det kræver 96 times at nå normtiden.

Rengøring af en operationsstue

En ny serviceassistent bruger 45 minutter første gang. Normtiden er 25, og læringsraten er 80 %.

Time first occasion
45 min
Learning rate (time at doubling as % of before)
80 %
Repetition you want to see time for
10 times
Standard time for experienced
25 min

It means: 10. gang tager den 21.4 min, og hun er nede på normtiden efter 7 times. Hun sparer 23.6 min pr. gang i forhold til første gang.

Rule of thumb

Ved 80 % halveres tiden ca. for hver tredje fordobling (0,8³ ≈ 0,51).

How to check the answer

Tiden ved 2. gang skal være første gangs tid × læringsraten.