Ch2- Measures of location and spread

Question 1

Advantage of IQR over range

Answer 1

Spread w/o extreme values

Question 2

Coding for mean and standard variation

Answer 2

• mean: sub mean into x
• s.d. : ignore any constants

y= 2x-5
m: 2 (mean) -5
s.d. : 2σ

Question 3

Formula for summary stastic (Sxx)

Answer 3

Sxx = σ² x n

variance = Sxx/n

Question 4

State the assumption involved with using class midpoints to calculate an estimate of a mean from a grouped frequency table. (1)

Answer 4

assumes the values are uniformly distributed within the class(es).