The fact that young children's articulation problems often disappear by themselves over time ...

The fact that young children's articulation problems often disappear by themselves over time indicates why researchers must use ____in order to have internal validity.
 
  a. control groups
  b. informed consent
  c. objective measurement
  d. pre- and postmeasures
  e. statistical analysis

Ques. 2

Indicate whether the following hypotheses are necessarily ex post facto research or possible to perform with experimental research. The size of a discussion group affects the quality of the discussions.
 
  a. necessarily ex post facto research b. possible to do with experimental research

Ques. 3

A researcher wishes to study the effects of a concentrated remedial reading program on the reading achievement of disadvantaged children. A large number of children are available for assignment to groups. Since intelligence is an important relevant variable in any research on reading, the investigator wants to make sure that it is controlled as well as the reading pretest scores. What would be the most effective way for the researcher to control these variables?
 
  a. Set up groups and then check to make sure that there are no significant differences between the groups on intelligence and reading pretest scores.
  b. Randomly assign children to experimental and control groups.
  c. Match the children on intelligence test and reading pretest scores and then randomly assign the matched pairs to experimental and control groups.
  d. Randomly assign children to experimental and control groups and use intelligence test and reading pretest scores in an analysis of covariance.