What is the minimum set of test temperature values needed for complete boundary value analysis coverage for a thermostat?

To determine the minimum set of test temperature values needed for complete boundary value analysis coverage for a thermostat, it's important to understand the principles of boundary value analysis. This technique is used to identify errors at the boundaries rather than within the ranges.

In the context of a thermostat, if we assume the valid operating temperature range is between 70°F and 75°F, then boundary values are those at and just outside the limits of this range. The boundaries to test would be at the edges of this range (70°F and 75°F) as well as just below and just above these boundaries, which are essential to ensure that the thermostat operates correctly at all critical points.

For option C, the values 69, 70, 75, and 76 include the boundary values of 70 and 75, along with the test values just outside those boundaries (69 and 76). This set effectively covers the critical boundaries needed for robust testing, ensuring that both the lower and upper limits of the thermostat's functionality are evaluated.

Testing at these boundary values allows us to confirm that the thermostat behaves correctly when the temperatures are at the edge of its specifications, as well as when they exceed those specifications. The other options do not provide a complete set