- WELCOME TO A LESSON ON EXPERIMENTS AND CONTROL GROUPS.
IN THIS LESSON WE WILL DEFINE CONTROL GROUPS,
DEFINE A PLACEBO AND THE PLACEBO EFFECT
AND ALSO DEFINE BLIND STUDIES.
FOR REVIEW FROM OUR PREVIOUS LESSON,
CONFOUNDING OCCURS
WHEN THERE ARE TWO OR MORE POTENTIAL VARIABLES
THAT COULD HAVE CAUSED THE OUTCOME,
AND IT IS NOT POSSIBLE TO DETERMINE
WHICH ACTUALLY CAUSED THE RESULT.
FOR EXAMPLE, RESEARCHERS WANT TO MEASURE THE EFFECTIVENESS
OF AN ENERGY DRINK ON MENTAL CONCENTRATION.
THEY ASK PARTICIPANTS TO COMPLETE A PUZZLE.
THEN AFTER CONSUMING THE DRINK, THEY COMPLETE A SECOND PUZZLE.
THE PARTICIPANTS COMPLETE THE SECOND PUZZLE FASTER.
HOWEVER, IT IS UNCLEAR
IF THE DRINK IMPROVED THE TIME TO COMPLETE THE PUZZLE
OR THE PRACTICE WITH THE FIRST PUZZLE.
SO BECAUSE THE VARIABLE CAUSING THE OUTCOME
CANNOT BE SPECIFICALLY DETERMINED, THIS IS CONFOUNDING.
THERE ARE A NUMBER OF MEASURES THAT CAN BE INTRODUCED
TO HELP REDUCE THE LIKELIHOOD OF CONFOUNDING.
THE PRIMARY MEASURE IS TO USE WHAT'S CALLED A CONTROL GROUP.
WHEN USING A CONTROL GROUP,
THE PARTICIPANTS ARE DIVIDED INTO TWO OR MORE GROUPS:
TYPICALLY, A CONTROL GROUP AND A TREATMENT GROUP,
WHERE THE TREATMENT GROUP RECEIVES THE TREATMENT
BEING TESTED.
THE CONTROL GROUP DOES NOT RECEIVE THE TREATMENT.
IDEALLY, THE GROUPS ARE OTHERWISE
AS SIMILAR AS POSSIBLE,
ISOLATING THE TREATMENT
AS THE ONLY POTENTIAL SOURCE OF DIFFERENCE BETWEEN THE GROUPS.
FOR THIS REASON, THE METHOD OF DIVIDING THE GROUPS
IS IMPORTANT.
SOME RESEARCHERS ATTEMPT TO ENSURE
THAT THE GROUPS HAVE SIMILAR CHARACTERISTICS,
BUT IT IS NEARLY IMPOSSIBLE TO CONTROL EVERY CHARACTERISTIC.
BECAUSE OF THIS,
RANDOM ASSIGNMENT IS VERY COMMONLY USED.
LET'S TAKE A LOOK AT AN EXAMPLE.
TO DETERMINE IF A ONE-DAY MATH REFRESHER CLASS
INCREASES A STUDENT'S MATH PLACEMENT SCORE,
THOSE NEEDING TO TAKE THE MATH PLACEMENT TEST
ARE RANDOMLY DIVIDED INTO TWO GROUPS.
ONE GROUP TAKES THE ONE-DAY MATH REFRESHER CLASS.
THE SECOND GROUP DOES NOT TAKE THE MATH REFRESHER CLASS.
SO IN THIS CASE, THE TREATMENT WOULD BE THE REFRESHER CLASS.
THE TREATMENT GROUP IS THE GROUP THAT TAKES THE REFRESHER CLASS,
AND THE CONTROL GROUP IS THE GROUP
THAT DOES NOT TAKE THE REFRESHER CLASS.
SOMETIMES NOT GIVING THE CONTROL GROUP ANYTHING
DOES NOT COMPLETELY CONTROL FOR CONFOUNDING VARIABLES.
FOR EXAMPLE, SUPPOSE A MEDICINE STUDY
IS TESTING A NEW HEADACHE PILL
BY GIVING THE TREATMENT GROUP THE PILL
AND THE CONTROL GROUP NOTHING.
IF THE TREATMENT GROUP SHOWED IMPROVEMENT,
WE WOULD NOT KNOW WHETHER IT WAS DUE TO THE MEDICINE IN THE PILL
OR A RESPONSE TO HAVE TAKEN ANY PILL,
AND THIS IS CALLED THE PLACEBO EFFECT.
WELL, THE PLACEBO EFFECT IS WHEN THE EFFECTIVENESS OF A TREATMENT
IS INFLUENCED BY THE PATIENT'S PERCEPTION
OF HOW EFFECTIVE THEY THINK THE TREATMENT WILL BE.
A POSITIVE RESULT IS EXPERIENCED
BECAUSE THE PATIENT BELIEVES
THEY ARE RECEIVING A USEFUL TREATMENT.
SO TO CONTROL THE PLACEBO EFFECT,
A PLACEBO OR DUMMY TREATMENT
THAT LOOKS JUST LIKE THE REAL TREATMENT
BUT DOESN'T HAVE THE ACTIVE INGREDIENT
IS OFTEN GIVEN TO THE CONTROL GROUP.
THIS WAY, BOTH GROUPS ARE TRULY IDENTICAL
EXCEPT FOR THE SPECIFIC TREATMENT GIVEN.
SO A PLACEBO IS A DUMMY TREATMENT GIVEN TO CONTROL
FOR THE PLACEBO EFFECT,
AND AN EXPERIMENT THAT GIVES THE CONTROL GROUP A PLACEBO
IS CALLED A PLACEBO CONTROLLED EXPERIMENT.
IN SOME CASES, THOUGH, IT IS MORE APPROPRIATE TO COMPARE
TO A CONVENTIONAL TREATMENT THAN A PLACEBO.
FOR EXAMPLE, IN A CANCER RESEARCH STUDY,
IT WOULD NOT BE ETHICAL TO DENY ANY TREATMENT
TO THE CONTROL GROUP
OR TO GIVE A PLACEBO TREATMENT.
IN THIS CASE, THE CURRENTLY ACCEPTABLE MEDICINE
WOULD BE GIVEN TO THE SECOND GROUP
NOW CALLED A COMPARISON GROUP.
IN OUR MATH PLACEMENT TEST EXAMPLE,
THE NON-TREATMENT GROUP WOULD MOST LIKELY BE ENCOURAGED
TO STUDY ON THEIR OWN
RATHER THAN BE ASKED TO NOT STUDY AT ALL
TO PROVIDE A MEANINGFUL COMPARISON.
WHEN USING A PLACEBO, IT WOULD DEFEAT THE PURPOSE
IF THE PARTICIPANT KNEW THEY WERE RECEIVING THE PLACEBO.
THE STUDY MUST BE WHAT'S CALLED A BLIND STUDY.
A BLIND STUDY OR SINGLE BLIND STUDY IS ONE
IN WHICH THE PARTICIPANT DOES NOT KNOW
WHETHER OR NOT THEY ARE RECEIVING THE TREATMENT
OR A PLACEBO.
A DOUBLE BLIND STUDY IS ONE IN WHICH THE PARTICIPANTS
AND THOSE INTERACTING WITH THE PARTICIPANTS
DON'T KNOW WHO IS IN THE TREATMENT GROUP
AND WHO IS IN THE CONTROL GROUP.
IT SHOULD BE NOTED THAT NOT ALL EXPERIMENTS
NEED A CONTROL GROUP.
IF THE RESEARCHER IS TESTING WHETHER A NEW MATERIAL
IS WATERPROOF,
THEY CAN SIMPLY PERFORM A WATERPROOF TEST.
THERE IS NO NEED FOR A CONTROL GROUP.
LET'S TAKE A LOOK AT AN EXAMPLE.
A TEAM OF RESEARCHERS IS TESTING THE EFFECTIVENESS
OF A NEW HPV VACCINE.
THEY RANDOMLY DIVIDE THE SUBJECTS INTO TWO GROUPS.
GROUP ONE RECEIVES EXISTING HPV VACCINE,
AND GROUP TWO RECEIVES A NEW HPV VACCINE.
NEITHER THE PATIENTS OR THE DOCTORS EXAMINING THEM
KNEW WHICH GROUP THEY WERE IN.
WE WANT TO DETERMINE WHICH IS THE TREATMENT GROUP,
WHICH IS THE CONTROL GROUP,
DETERMINE WHETHER THE STUDY IS BLIND, DOUBLE BLIND
OR NEITHER,
AND THEN WHICH BEST DESCRIBES THIS RESEARCH.
SINCE THIS STUDY IS DESIGNED TO DETERMINE
HOW EFFECTIVE THE NEW VACCINE WOULD BE,
THE TREATMENT GROUP WOULD BE THE GROUP RECEIVING THE NEW VACCINE,
WHICH IS GROUP TWO.
THE CONTROL GROUP IN THIS CASE WOULD BE THE GROUP
THAT RECEIVES THE EXISTING VACCINE,
WHICH WOULD BE GROUP ONE.
IN THIS CASE,
BECAUSE GROUP ONE IS RECEIVING AN ACCEPTABLE VACCINE,
WE COULD ALSO CALL THIS THE COMPARISON GROUP,
AND THE NEXT QUESTION,
"IS THIS STUDY BLIND, DOUBLE BLIND OR NEITHER?"
IT SAYS RIGHT HERE,
"NEITHER THE PATIENTS OR THE DOCTORS EXAMINING THEM
KNEW WHICH GROUP THEY WERE IN,"
WHICH MEANS THIS WOULD BE A DOUBLE BLIND STUDY.
AND THE LAST QUESTION ASKS US,
"WHICH BEST DESCRIBES THIS RESEARCH?"
THIS IS ACTUALLY A MULTIPLE CHOICE QUESTION.
SO LET'S LOOK AT OUR CHOICES.
WE SHOULD BE ABLE TO RECOGNIZE THAT THIS IS NOT A SURVEY,
AND WHILE IT COULD BE CONSIDERED A CLINICAL STUDY
AS WELL AS AN EXPERIMENT,
WE WANT THE BEST CHOICE.
SO LET'S FOCUS ON THESE TWO.
WE HAVE PLACEBO-CONTROLLED EXPERIMENT
AND A CONTROLLED EXPERIMENT.
REMEMBER, A CONTROLLED EXPERIMENT HAS A CONTROL GROUP
AND A TREATMENT GROUP.
SO WE DO HAVE A CONTROLLED EXPERIMENT,
BUT WE DON'T HAVE A PLACEBO-CONTROLLED EXPERIMENT,
BECAUSE REMEMBER, GROUP ONE IS NOT RECEIVING A PLACEBO,
MEANING A TREATMENT WITH NO MEDICATION AT ALL.
THEY'RE ACTUALLY RECEIVING THE TRADITIONAL VACCINE,
AND THEREFORE, THE BEST ANSWER WOULD BE
THIS IS A CONTROLLED EXPERIMENT.
IT'S NOT A PLACEBO-CONTROLLED EXPERIMENT,
BECAUSE AGAIN, NOTICE HOW GROUP ONE IS RECEIVING MEDICATION.
THEY'RE RECEIVING THE EXISTING HPV VACCINE.
SO THE BEST CHOICE IS A CONTROLLED EXPERIMENT.
I HOPE YOU FOUND THIS HELPFUL.