Topic 3: intro to measurment of basic summary stats

Question 1

Define measure of central tendency

Answer 1

• Single/central/typical value for given variable around which other values cluster

Question 2

Give examples of central tendency

Answer 2

• Mean
• Median
• Mode

Question 3

Define measure of dispersion

Answer 3

• Extent of spread of values of given variable

Question 4

Give examples of dispersion

Answer 4

• Variation
• SD
• Interquartile range

Question 5

Describe mode

Answer 5

• Most common value of variable
• Highest frequency in sample

Question 6

Describe median

Answer 6

• Middle point of a distribution

Question 7

Describe the mean

Answer 7

• Add all the values > divide by number of values
• In normal distribution = most values clustered around mean

Question 8

Describe range

Answer 8

• Largest value - smallest value
• Easy to compute
• Not very informative = considers only 2 observations = effected by extreme values

Question 9

Describe quantiles

Answer 9

• Solve the problem of range only having 2 values
• Sorts values from min-max then split into parts
• Tertiles = 3 categories
• Quartiles = 4 categories
• Quintiles = 5 categories
• Q1 = 25%
• Q2 = 50% median
• Q3 = 75%
• Interquartile range = Q3-Q1

Question 10

Describe SD

Answer 10

• Used to quantify spread of variation around mean cluster
• S = square root of variance
  FROM GRAPH
• Calculate mean
• Calculate how much each point deviates from mean
• Calculate average of deviations
• SD = how much data differs from mean on average

Question 11

Describe a box plot

Answer 11

• 5-number summary
  1) Min
  2) Q1
  3) Median
  4) Q3
  5) Max

Question 12

Describe histogram

Answer 12

• Summary graph for single numeric variable
• Use = understand pattern of variability in data
• Range of values = divided into equal intervals
• Shows = number of individual data points in each interval