MISSING DATA

:: Missing Data

Missing Data

Missing observations where it is not

possible to obtain valid measurements

on some of the experimental units

PROBLEM

:: Missing Data

Missing Data

• plants are destroyed

• animals die

• equipment malfunctioned

• errors in recording/transcription

• recorded data are lost

Possible causes (not as a result of treatment)

:: Missing Data

Missing Data

Major difficulties

1. Loss of information

2. Non-applicability of the standard

analysis of variance

:: Missing Data

Missing Data

Definition of missing values and

remedies to be suggested to specifically

exclude cases where recordings are not

made because of a treatment effect.

IMPORTANT

:: Missing Data

Defining missing values

Obj: Assess resistance of different varieties to a virus

Observation = zero or missing

If plant dies due to susceptibility to virus A:

grain yield = zero (0)

If plant dies and virus A has nothing to do

with it: grain yield = missing (.)

:: Missing Data

Defining missing values

Fertilizers: Mixture A, Mixture B, Mixture C

Observation = zero or missing

both A&B applied:

grain yield = missing (.)

correct mixture was

applied to the plant and

plant dies:

grain yield = zero (0)

CAB

ABCA