A calibration experiment was conducted to develop an appropriate protocol for an experimental procedure. The study tested three preparation methods (Prep) and four initial concentrations (Conc), combined in a completely randomized design with two replicates per combination. Absorbance values were measured for each solution after application to an ELISA plate and are recorded in the dataset. The data comprise the measured absorbances (Absorbance), the preparation method, and the initial concentration for each unit. One observation (unit 9) was excluded from analysis due to suspected contamination and was marked as missing.
Format
A data frame with 4 variables: Unit, Prep, Conc, Absorbance.
- Unit
Factor. Unique identifier for each observation or experimental unit.
- Prep
Factor. Preparation method applied to the sample.
- Conc
Factor. Initial concentration applied to the sample.
- Absorbance
Numeric. Measured absorbance value for each sample unit (may contain missing values for invalid readings).
Source
Welham, S. J., Gezan, S. A., Clark, S. J., and Mead, A. (2015) Statistical Methods in Biology: Design and analysis of experiments and regression
Examples
fit <- lm(log(Absorbance) ~ Prep * Conc,
data = calibrate |>
subset(!is.na(Absorbance)))
anova(fit)
#> Analysis of Variance Table
#>
#> Response: log(Absorbance)
#> Df Sum Sq Mean Sq F value Pr(>F)
#> Prep 2 0.5684 0.2842 1.2132 0.3312300
#> Conc 3 9.9835 3.3278 14.2063 0.0002971 ***
#> Prep:Conc 6 2.4999 0.4167 1.7787 0.1863825
#> Residuals 12 2.8110 0.2343
#> ---
#> Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1