L15 - Descriptive Statistics Flashcards
what are DESCRIPTIVE STATISTICS?
DESCRIPTIVE STATISTICS ANALYSE DATA to help DESCRIBE, SHOW or SUMMARISE it in a MEANINGFUL WAY.
Examples are MEASURES OF CENTRAL TENDENCY and MEASURES OF DISPERSION
what are MEASURES of CENTRAL TENDENCY?
MEASURES OF CENTRAL TENDENCY inform us about CENTRAL VALUES FOR A SET OF DATA. They are AVERAGES - ways of calculating a TYPICAL VALUE FOR A SET OF DATA
The AVERAGE can be CALCULATED IN DIFFERENT WAYS, EACH ONE APPROPRIATE FOR A DIFFERENT SITUATION
what is the MEAN? (MEASURES OF CENTRAL TENDENCY)
The MEAN is calculated by ADDING ALL THE SCORES and DIVIDING BY THE NUMBER OF SCORES
The ADVANTAGE of this method is that is REPRESENTATIVE of ALL THE DATA collected as it is CALCULATED USING ALL THE INDIVIDUAL VALUES
The mean is the MOST SENSITIVE MEASURE OF CENTRAL TENDENCY as it uses ALL THE VALUES in a set of data. However, the DISADVANTAGE is that it can be DISTORTED BY A SINGLE EXTREME VALUE in the set and the mean score MAY NOT BE ONE OF THE ACTUAL SCORES IN THE SET
what is the MEDIAN? (MEASURES OF CENTRAL TENDENCY)
The MEDIAN is calculated by ARRANGING THE SCORES in ORDER then CHOOSING THE NUMERICAL MIDPOINT
The ADVANTAGE is that its UNAFFECTED BY EXTREME SCORES, UNLIKE THE MEAN
The DISADVANTAGE is that ANY EXTREME VALUES would NOT FORM PART OF THE AVERAGE MEASUREMENT. It is LESS SENSITIVE than the MEAN, it DOES NOT REPRESENT ALL THE FINDINGS
what is the MODE?
The MODE is the MOST FREQUENT VALUE in A SET
The ADVANTAGE is that its UNAFFECTED BY EXTREME SCORES
The DISADVANTAGE is that it TELLS US NOTHING ABOUT THE OTHER SCORES IN THE DATA SET
what are MEASURES OF DISPERSION?
A SET OF DATA can also be described in terms of HOW DISPERSED OR SPREAD OUT THE DATA ITEMS ARE
what is the RANGE?
the RANGE is calculated by TAKING THE LOWEST SCORE AWAY FROM THE HIGHEST
An ADVANTAGE of this is that it is QUICK AND EASY TO CALCULATE.
A DISADVANTAGE is that it can be EASILY DISTORTED BY EXTREME VALUES
what is the STANDARD DEVIATION?
The STANDARD DEVIATION is the AVERAGE AMOUNT that EACH SCORE DIFFERS FROM THE MEAN
An ADVANTAGE is that it TAKES ACCOUNT OF ALL THE SCORES.
A DISADVANTAGE is that it is MORE DIFFICULT TO CALCULATE THAN THE RANGE
what are PERCENTAGES?
To calculate PERCENTAGES first take the NUMBER OF PPS IN A CONDITION and DIVIDE BY THE TOTAL NUMBER OF PPS.
Then MULTIPLY THE NUMBER BY 100
E.g 4 OUT OF 10 people SMOKE in a STUDY, (4/10) X 100 = 40%
