How Many Observations Should Be Taken to Be 90% Confident

question 22

Multiple Choice

How many observations should be taken to be 90% confident of being within +2% of the actual time a machine is busy if it is believed that the machine is in use 70% of the time?

• A)2,021 observations
• B)1,421 observations
• C)789 observations
• D)365 observations

---

Definitions:

Lubricating Film

A thin layer of liquid or other substances applied to surfaces to reduce friction and wear.

Smooth Surface

A type of physical surface that is even and untextured, often found in manufactured objects and natural formations.

Synovial Membrane

The soft tissue that lines the inner surface of synovial joints, producing synovial fluid for lubrication.

Lubricating Film

A thin layer of liquid or substance applied to surfaces to minimize friction and wear, commonly found in mechanical systems, joints, and tissues.