## STAM101 :: Lecture 21 :: Split plot design – layout – ANOVA Table Split-plot Design
In field experiments certain factors may require larger plots than for others. For example, experiments on irrigation, tillage, etc requires larger areas. On the other hand experiments on fertilizers, etc may not require larger areas. To accommodate factors which require different sizes of experimental plots in the same experiment, split plot design has been evolved.
In this design, larger plots are taken for the factor which requires larger plots. Next each of the larger plots is split into smaller plots to accommodate the other factor. The different treatments are allotted at random to their respective plots. Such arrangement is called split plot design.
In split plot design the larger plots are called main plots and smaller plots within the larger plots are called as sub plots. The factor levels allotted to the main plots are main plot treatments and the factor levels allotted to sub plots are called as sub plot treatments.

Layout and analysis of variance table
First the main plot treatment and sub plot treatment are usually decided based on the needed precision. The factor for which greater precision is required is assigned to the sub plots.
The replication is then divided into number of main plots equivalent to main plot treatments. Each main plot is divided into subplots depending on the number of sub plot treatments. The main plot treatments are allocated at random to the main plots as in the case of RBD. Within each main plot the sub plot treatments are allocated at random as in the case of RBD. Thus randomization is done in two stages. The same procedure is followed for all the replications independently.

The analysis of variance will have two parts, which correspond to the main plots and sub-plots. For the main plot analysis, replication X main plot treatments table is formed. From this two-way table sum of squares for replication, main plot treatments and error (a) are computed. For the analysis of sub-plot treatments, main plot X sub-plot treatments table is formed. From this table the sums of squares for sub-plot treatments and interaction between main plot and sub-plot treatments are computed. Error (b) sum of squares is found out by residual method. The analysis of variance table for a split plot design with m main plot treatments and s sub-plot treatments is given below.

Analysis of variance for split plot with factor A with m levels in main plots and factor B with s levels in sub-plots will be as follows:

 Sources of                                                                           Variation d.f. SS MS F Replication r-1 RSS RMS RMS/EMS (a) A m-1 ASS AMS AMS/EMS (a) Error (a) (r-1) (m-1) ESS (a) EMS (a) B s-1 BSS BMS BMS/EMS (b) AB (m-1) (s-1) ABSS ABMS ABMS/EMS (b) Error (b) m(r-1) (s-1) ESS (b) EMS (b) Total                   rms – 1                 TSS

Analysis
Arrange the results as follows

 Treatment Combination Replication Total R1 R2 R3 … A0B0 a0b0 a0b0 a0b0 … T00 A0B1 a0b1 a0b1 a0b1 … T01 A0B2 a0b2 a0b2 a0b2 … T02 Sub Total A01 A02 A03 … T0 A1B0 a1b0 a1b0 a1b0 … T10 A1B1 a1b1 a1b1 a1b1 … T11 A1B2 a1b2 a1b2 a1b2 … T12 Sub Total A11 A12 A13 … T1 . . . . . . . . . . . . . . . . . . Total R1 R2 R3 … G.T TSS=[ (a0b0)2 + (a0b1)2+(a0b2)2+…]-CF

Form A x R Table and calculate RSS, ASS and Error (a) SS

 Treatment Replication Total R1 R2 R3 … A0 A01 A02 A03 … T0 A1 A11 A12 A13 … T1 A2 A21 A22 A23 … T2 . . . . . . . . . . . . . . . . . . Total R1 R2 R3 … GT   Error (a) SS= A x R TSS-RASS-ASS.
Form A xB Table and calculate BSS, Ax B SSS and Error (b) SS

 Treatment Replication Total B0 B1 B2 … A0 T00 T01 T02 … T0 A1 T10 T11 T12 … T1 A2 T20 T21 T22 … T2 . . . . . . . . . . . . . . . . . . Total C0 C1 C2 … GT  ABSS= A x B Table SS – ASS- ABSS
Error (b) SS= Table SS-ASS-BSS-ABSS –Error (a) SS.
Then complete the ANOVA table. Download this lecture as PDF here 