A ____________ is a threat to internal validity when groups in an ...

[maegan_martin]

A ____________ is a threat to internal validity when groups in an experiment are not equivalent at the beginning of the experiment with regard to the dependent variable.
 
  a. beginning error
  b. selection error
  c. pretest error
  d. selection bias
  e. experimental bias

Question 2

The ________ technique is used particularly in ecological studies in order to estimate the size of unknown populations.
 
  Fill in the blank(s) with correct word

[joneynes]

Answer to Question 1

D

Answer to Question 2

Mark recapture or tag and release

[maegan_martin]

Thanks for the timely response, appreciate it

[sultansheikh]

Wow, this really help