A researcher is comparing three new formulas for grass killer. To conduct the experiment, the researcher purchases 30 pieces of sod from various vendors to use in the study. The 30 pieces of sod are laid out in three different areas. The researcher places three slips of paper in a bowl labeled formula 1, formula 2, and formula 3 and randomly picks a piece of paper to apply that formula to the sod in the first area. Then the researcher picks again and applies that formula to the second area. Finally, the last formula is used on the last area. Which component is missing from the researcher’s process?

The researcher should not have laid out the pieces of sod in different areas.
The researcher did not randomly assign the pieces of sod to the treatment groups.
The researcher did not randomly pick the vendors when purchasing the pieces of sod.
The researcher did not use randomization when selecting the pieces of sod from the vendors.