Overview of Probit Analysis

Use Probit Analysis to estimate the number of units that you can expect to fail in response to a certain amount of stress or stimulus.

Probit analysis examines the relationship between a binary response variable and a continuous stress variable. To perform the analysis, you impose a stress (or stimulus) on a number of units, and then record whether each unit either breaks (defined as an event) or withstands the stress. Based on the sample data, Minitab calculates a probit equation that you can use to do the following:
• Examine how the probability of an event changes as the stress variables change
• Predict the probability of an event for any stress value in the experimental range

In the life sciences, probit analysis can be used to evaluate whether an organism is likely to survive when subjected to various levels of physical or environmental stress. For example, a wildlife researcher wants to determine at what concentration a pollutant kills 50% of fish. An entomologist wants to know the probability that an insect will die when exposed to a certain amount of pesticide.

In the engineering sciences, probit analysis can be used with destructive testing. For example, an engineer wants to determine how well submarine hull materials perform when they are exposed to underwater explosions. The engineer subjects the materials to various magnitudes of explosions, and then records whether or not the hull cracks. The engineer uses probit analysis to determine at what shock level 10% of the hulls can be expected to crack.

Where to find this analysis

To perform a probit analysis, choose Stat > Reliability/Survival > Probit Analysis.

When to use an alternate analysis

If your response data are continuous measurements of failure time (or other units), instead of binary values with only two possible outcomes, use Accelerated Life Testing.

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