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Options

Worked examples

The How-To pages build this chart step by step from sample data, one walkthrough per data layout the tool accepts. Start there if you would rather see a finished result than read the settings.

Every control on the Options tab sits in one group, Tolerance Interval Options.

These two boxes take a proportion, not a percent

Type 0.95, not 95. Both boxes changed from a percent to a proportion, so they now match the other controls of their kind across the product. A value outside the range is refused rather than quietly corrected, with a message box titled Tolerance Interval reading: The confidence level must be a number greater than 0 and less than 1. It is a proportion, not a percent, so type 0.95 for 95 percent. The same sentence names the proportion of the population when it is that box you got wrong.

Confidence level:

How sure you want to be that the interval really does contain the proportion you asked for. A proportion strictly between 0 and 1, written \(C\) on the Math Details page.

Only 0 and 1 themselves are refused, along with anything outside them. A confidence of 0.999999999999 is accepted.

Proportion of population:

The least share of the population the interval has to contain, written \(P\) on the Math Details page. A proportion strictly between 0 and 1, on the same terms as the box above.

These two are easy to confuse and they answer different questions. The proportion of population is how much of the product you want the interval to cover. The confidence level is how sure you are that it does.

Interval side:

Three radio buttons:

  • Two-sided: a lower and an upper bound that together contain the proportion.
  • One-sided lower bound: a lower bound such that at least the stated proportion lies above it.
  • One-sided upper bound: an upper bound such that at least the stated proportion lies below it.

Pick the side your specification has. A characteristic with a minimum and no maximum wants a one-sided lower bound, and asking for two bounds on it widens the interval for no reason.

See Also