The best replacement for investigation is experiment.

The best alternatives to investigation are rated as following:
★★★★★  experiment
★★★★  inquiry
★★  research
★★  audit
★  investigations
★  interrogation
★  cooperative learning
★  underworld trading
★  probe
★  homicide investigation
  enquiry
  scientific method
  investigative
  soil exploration
  examination
  public investigation
  private investigation
  inquest
  treasure hunting
  commander's inquiry
  standard investigation
  scientific inquiry
  cbp background investigation
  slicing
  preliminary investigation
  fbi
  internal investigation

Your alternative for investigation is not listed? Suggest!
Speaking about investigation, one probably shouldn't forget about suspension.

Other search terms related to investigation and their ratings are:
★★★★★ suspension
★★★★★ odd and even numbers
You have in mind a companion for investigation and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of investigation in all years. Click on graph for more.
investigation
experiment
inquiry