descriptive statistics

Question 1

measures of central tendency

Answer 1

tell us about the central most typical value in a data set

mean
median
mode

Question 2

evaluate the use of the mean

Answer 2

+ most representative as it is comprised of the whole data set

– can be distorted by outliers, can only be used with ordinal and interval data

Question 3

evaluate the use of the median

Answer 3

+ not distorted by outliers

– doesn’t reflect all scores in the data set

Question 4

evaluate the use of the mode

Answer 4

+ not distorted by outliers, the only one that can be used with nominal data

– can be more than one or no mode so isn’t always useful

Question 5

measures of dispersion

Answer 5

define the spread of data around a central value (mean or median)

range
standard deviation

Question 6

evaluate the use of the range

Answer 6

+ easy to calculate

– doesn’t indicate the distribution pattern across the whole data set

Question 7

standard deviation

Answer 7

• how far scores deviate from the mean
• high sd = very dispersed around the mean (e.g. people scored very differently)
• low sd = very concentrated around the mean (e.g. people scored very similarly)

Question 8

evaluate the use of standard deviation

Answer 8

+ is precise as all data values are included in the calculation

– can be distorted by outliers

Question 9

percentages calculation

Answer 9

e.g.

(no. of participants who improved/total no. of participants) x 100

Question 10

percentage increase

Answer 10

(increase/original) x 100

Question 11

percentage decrease

Answer 11

(decrease/original) x 100