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- WELCOME TO AN INTRODUCTORY LESSON ON EXPERIMENTS
AND CONFOUNDING.
SO FAR WE HAVE PRIMARILY DISCUSSED OBSERVATIONAL STUDIES.
THESE ARE STUDIES IN WHICH CONCLUSIONS WOULD BE DRAWN
FROM OBSERVATIONS OF A SAMPLE OR THE POPULATION.
IN SOME CASES,
THESE OBSERVATIONS MIGHT BE UNSOLICITED,
SUCH AS STUDYING THE PERCENTAGE OF CARS
THAT DON'T SLOW DOWN IN A SCHOOL ZONE.
IN OTHER CASES, THE OBSERVATIONS ARE SOLICITED,
LIKE IN A SURVEY OR POLL.
IN CONTRAST, IT IS COMMON TO USE EXPERIMENTS
WHEN EXPLORING HOW SUBJECTS REACT TO AN OUTSIDE INFLUENCE.
IN AN EXPERIMENT,
SOME KIND OF TREATMENT IS APPLIED TO THE SUBJECTS,
AND THE RESULTS ARE MEASURED.
SO AN OBSERVATIONAL STUDY IS A STUDY BASED ON OBSERVATIONS
OR MEASUREMENTS,
AND AN EXPERIMENT IS A STUDY IN WHICH THE EFFECTS OF A TREATMENT
ARE MEASURED.
LET'S LOOK AT SOME EXAMPLES OF EXPERIMENTS.
A PHARMACEUTICAL COMPANY TESTS A NEW ANTI-AGING CREAM
BY ADMINISTERING THE CREAM TO 100 ELDERLY PATIENTS.
THE TREATMENT HERE WOULD BE THE ANTI-AGING CREAM.
YOU TEST A NEW LAUNDRY DETERGENT BY BUYING A BOTTLE
AND DOING YOUR LAUNDRY.
THE NEW CLEANER OR DETERGENT IS THE TREATMENT.
A PSYCHOLOGY RESEARCHER
EXPLORES THE EFFECTS OF A VIOLENT VIDEO GAME
BY MEASURING PEOPLE'S TEMPERAMENT
WHILE PLAYING THE GAME.
HERE THE VIDEO GAME IS THE TREATMENT.
A DIETICIAN TESTS OUT A NEW RECIPE TO LOWER CHOLESTEROL.
THE TREATMENT HERE WOULD BE THE NEW RECIPE.
IN CONTRAST, THE HEIGHT AND WEIGHT
OF 100 RANDOMLY SELECTED GYM MEMBERS ARE MEASURED.
THIS IS AN OBSERVATIONAL STUDY, NOT AN EXPERIMENT.
SO WE HAVE FOUR EXAMPLES OF EXPERIMENTS
AND ONE EXAMPLE OF AN OBSERVATIONAL STUDY.
WHEN CONDUCTING EXPERIMENTS,
IT IS ESSENTIAL TO ISOLATE THE TREATMENT BEING TESTED.
SUPPOSE THE SUCCESS RATES IN DEVELOPMENTAL MATH
AT A COMMUNITY COLLEGE ARE NOT GOOD.
AS A RESULT, THE MATH DEPARTMENT DECIDES TO PILOT
A NEW MATH PROGRAM
AND HIRES A NEW INSTRUCTOR TO TEACH THE PROGRAM.
IF THE NEW PROGRAM IS SUCCESSFUL,
WHAT IS RESPONSIBLE FOR THE IMPROVEMENT,
THE NEW CURRICULUM OR THE NEW INSTRUCTOR?
THIS IS CALLED CONFOUNDING
WHEN IT IS NOT CLEAR WHICH FACTOR OR FACTORS
CAUSED THE OBSERVED EFFECT.
CONFOUNDING IS THE DOWNFALL OF MANY EXPERIMENTS,
THOUGH SOMETIMES IT CAN BE HIDDEN.
SO 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.
ANOTHER EXAMPLE OF CONFOUNDING WOULD BE IF A COMPANY CLAIMS
THAT THEIR GAS ADDITIVE IMPROVES GAS MILEAGE.
HOWEVER, IN THE DIRECTIONS OF THE STUDY,
DRIVERS ARE ALSO ENCOURAGED TO CHECK THEIR TIRE PRESSURE
AND NOT DRIVE AGGRESSIVELY
BY SUDDENLY ACCELERATING OR BREAKING.
IF THERE WAS AN INCREASE IN GAS MILEAGE,
IT WOULD BE UNCLEAR EXACTLY WHY.
IT COULD BE BECAUSE OF THE GAS ADDITIVE
OR BECAUSE OF THE OTHER RECOMMENDATIONS.
IN OUR NEXT LESSON,
WE WILL TALK ABOUT HOW CONTROL GROUPS CAN BE USED
TO REDUCE THE LIKELIHOOD OF CONFOUNDING.
I HOPE YOU FOUND THIS HELPFUL.