Answer: It will result in a systematic uncertainty. Therefore the final result will have a systematic error.
Explanation:
Systematic errors are those experimental errors that didn't occurs by chance or nature. Their are those errors that occur in any experiment, as a result of wrong measurements or observation. Because this students has taken a wrong measurements for the length of the pendulum, their results will be affected, though it will be similar to each other's result because all of them applied the same error. But if this practical is rerun, applying the correct measurement, the result Goten will be different from the results gotten by the students. The difference between this two result is called THE SYSTEMATIC UNCERTAINTY.