Answer: I.if the instruments used in the experiment were miscalibrated.
II.if the experiment did not include a control group
IV.if missing experimental data was estimated rather than measured.
Step-by-step explanation:
There are many reasons which can bring errors and mistakes in the data obtain after the experimental procedure which can yield conclusions which cannot be considered as valid.
The following are the examples of the cases which can bring incorrectness in the conclusion. For them the validity is required to be tested.
I.if the instruments used in the experiment were miscalibrated.: The instruments used in the experiment are miscaliberated they can yield inappropriate data hence, the conclusion will become incorrect and invalid.
II.if the experiment did not include a control group. : The control group is used to compare the variation and changes in the experimental group. If it is not used the experiment will be considered as invalid and the conclusion will also be invalid.
IV.if missing experimental data was estimated rather than measured. : The estimation can make the data manipulative rather then qualitative or quantitative. This will yield conclusion which will generated after manipulative efforts thus also questions on the validity of the results.