A field experiment was conducted using a completely randomized design to evaluate the effect of growth regulator application and oilseed rape variety (B or N) on seed production, with six replicates per treatment combination. During the trial, some plots were grazed by pigeons, raising concerns that this damage could influence plant growth and seed development. The percentage of each plot's area affected by bird grazing (variate Damage, recorded to the nearest 10 percent) was measured to allow for adjustment in the analysis. The main response variable was thousand grain weight (TGW), and treatment combinations reflect all four factorial combinations of growth regulator presence/absence and variety, coded as a single factor (Trt: +B, +N, -B, -N). The dataset enables investigation of the effects of variety and growth regulator on seed weight, while controlling for the confounding influence of bird grazing damage.
Format
A data frame with 6 variables: Plot, GR, Variety, Trt, Damage, TGW.
- Plot
Factor. Unique identifier for each experimental plot.
- GR
Factor. Growth regulator application: "+" (with growth regulator) or "-" (without growth regulator).
- Variety
Factor. Oilseed rape variety: "B" or "N".
- Trt
Factor. Treatment combination label indicating both growth regulator and variety (one of "+B", "+N", "-B", "-N").
- Damage
Integer. Percentage of plot area grazed by pigeons, recorded to the nearest 10 percent.
- TGW
Numeric. Thousand grain weight (TGW) response, measuring the average weight (in grams) of 1000 seeds from each plot.
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
lm(Damage ~ Trt, data = tgw)
#>
#> Call:
#> lm(formula = Damage ~ Trt, data = tgw)
#>
#> Coefficients:
#> (Intercept) Trt-N Trt+B Trt+N
#> 28.33 -5.00 -5.00 20.00
#>
lm(TGW ~ Damage * Trt, data = tgw)
#>
#> Call:
#> lm(formula = TGW ~ Damage * Trt, data = tgw)
#>
#> Coefficients:
#> (Intercept) Damage Trt-N Trt+B Trt+N
#> 3.16160 0.00702 1.60555 0.61957 1.91623
#> Damage:Trt-N Damage:Trt+B Damage:Trt+N
#> -0.02839 -0.01986 -0.03648
#>