M9: Lifetime determination

Question 1

What is the definition of service lifetime?

Answer 1

Time span a product is in use or hibernating.

Question 2

What is a lifetime distribution function and what is a survival function?

Answer 2

Lifetime distribution function: Probability distribution function describes the rate of exit at time t.

Survival function: Probability that the time of death TD(or exit of use) is later than some specified time t.

Question 3

Approach U.S. EPA used for calculating electronic waste

Answer 3

1.
Determine age distribution of collected products in April 2004 (20’619 products)

2. Use age distribution to estimate a lifetime distribution function
3. Use historic sales data and lifetime distribution function to calculate WEEE flow

Question 4

List the reasons for products reaching end of service life:

Answer 4

A) Deterioration –> diminishing functionality (wear out, run out, breakage…)

B) Obsolescence

• -> process of passing out of usefulness (disused or discarded)
• -> a product is no longer wanted even though it may still be in good working order.

Question 5

Mention the 4 categories of obsolescence:

Answer 5

1. Technical obsolescence
   New products or technologies supersede old ones
   –> CDs and CD players make cassettes and vinyl records obsolete
   –> newer, faster processors make older ones obsolete
2. Systemic or functional obsolescence
   System changes cause malfunction of products in new environment
   –> new Windows versions make old Office programs obsolete
   –> replacement parts are no longer available or too expensive
3. Style obsolescence
   Change in style makes products lose their appeal (independent of functionality)
   –> cloths, mobile phones, toys

4.Notification obsolescence
Obsolescence is predetermined in product design and customers are advised to replace products or parts to avoid health risks or maintain optimal performance
–> water filters