### Abstract

Language | English |
---|---|

Pages | 32-35 |

Number of pages | 4 |

Volume | 13 |

Specialist publication | Microbiologist |

Publication status | Published - Sep 2012 |

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### Keywords

- statistics
- fixed effects model
- variance ratio
- analysis of variance

### Cite this

*Microbiologist*,

*13*, 32-35.

}

*Microbiologist*, vol. 13, pp. 32-35.

**Statnote 30 : The one-way analysis of variance (ANOVA) : fixed effects model.** / Armstrong, Richard; Hilton, Anthony.

Research output: Contribution to specialist publication › Article

TY - GEN

T1 - Statnote 30 : The one-way analysis of variance (ANOVA)

T2 - Microbiologist

AU - Armstrong, Richard

AU - Hilton, Anthony

PY - 2012/9

Y1 - 2012/9

N2 - In Statnote 9, we described a one-way analysis of variance (ANOVA) ‘random effects’ model in which the objective was to estimate the degree of variation of a particular measurement and to compare different sources of variation in space and time. The illustrative scenario involved the role of computer keyboards in a University communal computer laboratory as a possible source of microbial contamination of the hands. The study estimated the aerobic colony count of ten selected keyboards with samples taken from two keys per keyboard determined at 9am and 5pm. This type of design is often referred to as a ‘nested’ or ‘hierarchical’ design and the ANOVA estimated the degree of variation: (1) between keyboards, (2) between keys within a keyboard, and (3) between sample times within a key. An alternative to this design is a 'fixed effects' model in which the objective is not to measure sources of variation per se but to estimate differences between specific groups or treatments, which are regarded as 'fixed' or discrete effects. This statnote describes two scenarios utilizing this type of analysis: (1) measuring the degree of bacterial contamination on 2p coins collected from three types of business property, viz., a butcher’s shop, a sandwich shop, and a newsagent and (2) the effectiveness of drugs in the treatment of a fungal eye infection.

AB - In Statnote 9, we described a one-way analysis of variance (ANOVA) ‘random effects’ model in which the objective was to estimate the degree of variation of a particular measurement and to compare different sources of variation in space and time. The illustrative scenario involved the role of computer keyboards in a University communal computer laboratory as a possible source of microbial contamination of the hands. The study estimated the aerobic colony count of ten selected keyboards with samples taken from two keys per keyboard determined at 9am and 5pm. This type of design is often referred to as a ‘nested’ or ‘hierarchical’ design and the ANOVA estimated the degree of variation: (1) between keyboards, (2) between keys within a keyboard, and (3) between sample times within a key. An alternative to this design is a 'fixed effects' model in which the objective is not to measure sources of variation per se but to estimate differences between specific groups or treatments, which are regarded as 'fixed' or discrete effects. This statnote describes two scenarios utilizing this type of analysis: (1) measuring the degree of bacterial contamination on 2p coins collected from three types of business property, viz., a butcher’s shop, a sandwich shop, and a newsagent and (2) the effectiveness of drugs in the treatment of a fungal eye infection.

KW - statistics

KW - fixed effects model

KW - variance ratio

KW - analysis of variance

UR - http://issuu.com/societyforappliedmicrobiology/docs/sept2012_micro

M3 - Article

VL - 13

SP - 32

EP - 35

JO - Microbiologist

JF - Microbiologist

SN - 1479-2699

ER -