What type of impact test involves the specimen being held vertically?

The Izod Test is the correct answer because it specifically requires the specimen to be held vertically during the impact testing procedure. In this test, a notched specimen is clamped at the bottom and struck at the top with a pendulum hammer. This vertical orientation is crucial as it mimics certain real-world applications where materials are subjected to lateral impacts. The key purpose of the Izod Test is to measure the material's resistance to impact forces, particularly in situations where the material may experience sudden shock loads.

In contrast, the Charpy Test typically positions the specimen horizontally, which allows for a different method of measuring the energy absorbed by the specimen during impact. The Compression Test and Tensile Test do not involve impact tests at all; instead, they focus on measuring the material's response to compressive and tensile forces, respectively. These tests evaluate different mechanical properties and are not concerned with impact resistance like the Izod and Charpy tests are.