GOOD DAY EVERYONE, TODAY I WILL DISSCUSS ABOUT HOW TO DETERMINE THE APPROPRIATE TOOL WHEN THE VARIANCE IS KNOWN, UNKNOWN, AND WHEN THE CENTRAL LIMIT THEOREM IS USED.
WHEN VARIANCE IS KNOWN:
WE USE Z-TEST AS THE APPROPRIATE TOOL WHEN THE VARIANCE IS KNOWN. IT IS USED TO VALIDATE A HYPOTHESIS THAT THE SAMPLE DRAWN BELONGS TO THE SAME POPULATION.
REMEMBER:
Z-TEST IS USED WHEN:THE POPULATION STANDARD DEVIATION IS KNOWNTHE SAMPLE IS ASSUMED TO BE NORMALLY DISTRIBUTEDTHE SAMPLE SIZE IS GREATER THAN OR EQUAL TO 30 (n ≥ 30)
WHEN VARIANCE IS UNKNOWN:
WE USE T-TEST IF THE VARIANCE IS UNKNOWN. THERE ARE ALSO THINGS THAT WE SHOULD REMEMBER WHEN USING T-TEST.REMEMBER:THE POPULATION STANDARD DEVIATION IS UNKNOWN.THE SAMPLE STANDARD DEVIATION IS KNOWN.THE SAMPLE IS NORMAL OR NEARLY NORMAL DISTRIBUTEDTHE SAMPLE SIZE IS LESS THAN 30 ( 30)
CENTRAL LIMIT THEOREM
LASTLY, WHEN THIS IS USED, WE MAY STILL USE Z-TEST BY REPLACING THE POPULATION STANDARD DEVIATION BY ITS ESTIMATE SAMPLE STANDARD DEVIATION.THINGS TO REMEMBER:VARIANCE IS KNOWN OR UNKNOWN.POPULATION MAY NOT BE NORMALLY DISTRIBUTED.THE SAMPLE SIZE IS CONSIDERED TO BE SUFFICIENTLY LARGE.
THANK YOU!
THAT'S ALL. THANK YOU FOR LISTENING AND I HOPE YOU HAVE LEARNED SOMETHING!