Tolerance Interval

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Tolerance Interval
Message posted by Bill Chamberlin on December 29, 1999 at 12:00 AM (ET)

I am searching for a layman's definition or explanation of the statistical term "tolerance" or "tolerance interval". Any help would be appreciated. Thanks.

READERS RESPOND:
(In chronological order. Most recent at the bottom.)

Re: Tolerance Interval
Message posted by nancy diehl on January 3, 2000 at 12:00 AM (ET)

The term tolerance and tolerance interval is used a lot in engineering
and manufacturing. It refers to a dimension and how much that dimension
is allowed to deviate from its preferred value. For example, an aircraft
blade may have a required dimension for its length to be 3.5". It's
virtually impossible to always cast these parts to exactly 3.5". A tolerance
comes with this length of let's say, +/- .25. The blade is unacceptable
if the length is less than 3.25 and greater than 3.75. As long as the
blade length falls between 3.25 and 3.75, the part is acceptable.

The tolerance is the .25, the interval is the +/- .25. The target is 3.5.
The tolerance interval in industry has been equated to represent
+/- 3sigma.

Re: Tolerance Interval
Message posted by Jack Tomsky on January 4, 2000 at 12:00 AM (ET)

A tolerance interval is an interval, calculated from the data, having the property that you have a specified degree of confidence (e. g., 95%) that the interval includes at least a specified percentage (e. g., 99%) of the population distribution. For the normal distribution, tolerance intervals are of the form, xbar +/- k*s.

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