A researcher conducts a quasi-experimental study to determine whether there is appropriate weight ...

A researcher conducts a quasi-experimental study to determine whether there is appropriate weight gain among premature infants who are fed according to cue-based protocols.
 
  The researcher trained neonatal intensive care nurses to apply cue-based feeding to orally fed infants and notes a statistical difference in weight gain between infants fed according to cue-based protocols and those fed according to standard protocols. The reviewer critiquing the study notes that not all nurses completed the cue-based feeding module. This would affect which type of validity?
  a. Construct validity
  b. External validity
  c. Internal validity
  d. Statistical conclusion validity