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Analyses of Variance.

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Presentation on theme: "Analyses of Variance."— Presentation transcript:

1 Analyses of Variance

2 Assumptions behind the ANOVA
Assumption of data being normally distributed. Homogeneity of error variance. Additivity of variance effects. Data collected from a properly randomized experiment.

3 Dealing with Wrongful Data
It is usually assumed that the data collected is correct!. Why would data not be correct? Mis-recording, mis-classification, transcription errors, errors in data entry. Outliers.

4 Dealing with Wrongful Data
What things can help? Keep detailed records, on each experimental unit. Decide beforehand what values would arouse suspision.

5 Dealing with Wrongful Data
What do you do with suspicios data? If correct, and it is discarded, then valuable information is lost. This will bias the results. If wrong and included, will bias results and may have extreme consequences.

6 Checking ANOVA Accurucy
Coefficient of variation: [e/]x100. CV=(√100.9/73.75)*100=13.6% R2 value = {[TSS-ESS]/TSS}x100. R2 = (1654/3654)*100 = 44.7%. Compare the effect of blocking or sub-blocking (discussed later).

7 Analyses of CRB Designs
Yij =  + ti eij

8 Analysis of Variance of CRB
Source df SS Between treatments k-1 [G12/n1 + G22/n2 … Gk2/nk] - CF Within treatments jk-k By difference Total jk-1 [x112 + x … + xjk2] - CF CF = [xij]2/jk

9 Example of Analysis of Variance
Source df SS MS F Between genotypes 3 2598.3 866.1 4.16 ** Within genotypes 12 2501.1 208.4 Total 23 3654.5 ** = 0.01 > P > 0.001

10 Analyses of RCB Designs
Yij =  + bi + tj + eij

11 Analysis of Variance of RCB
Source df SS Blocks r-1 [B12 + B22 + … + Br2]/t – CF Treatments t-1 [T12 + T22 + … + Tt2]/r – CF Error (r-1)(t-1) By difference Total rt-1 [x112 + x … + xrt2] – CF CF = [xij]2/rt

12 Example Treatment 1 2 3 4 Total T-1 330 288 295 313 1225 T-2 372 340
343 341 1396 T-3 359 337 373 302 1371 Totals 1061 965 1011 956 3993 CF = [3993]2/12 = 1,328,671 TSS = [ … ] – CF = 8,864

13 Example Treatment 1 2 3 4 Total T-1 330 288 295 313 1225 T-2 372 340
343 341 1396 T-3 359 337 373 302 1371 Totals 1061 965 1011 956 3993 Block SS = [ ]/3 – CF = 2,330 Treat SS = [ ]/4 – CF = 4,212

14 Analysis of Variance Source df SS MS F Blocks 3 2330 777 2.00 ns
Insecticides 2 4212 2106 5.44 * Error 6 2322 387 Total 11 8864 * = 0.05 > P > 0.01

15 Example Treatment 1 2 3 4 Mean T-1 330 288 295 313 306 T-2 372 340 343
341 349 T-3 359 337 373 302 sed[mean] = (2e2)/4 = (2 x 387)/4 = df se[mean] = (e2)/4 = (387/4) = df

16 Analyses of Latin Designs
Yijk =  + ri + cj + tk(ij) + eijk

17 Analysis of Variance of Latin
Source df SS Rows t-1 [R12 + R22 + … + Rt2]/t – CF Columns [C12 + C22 + … + Ct2]/t – CF Treatments [T12 + T22 + … + Tt2]/t – CF Error (t-1)(t-2) By difference Total t2-1 [x112 + x … + xtt2] – CF CF = [xij]2/t2

18 Example Row/Col 1 2 3 4 Total B-1.64 D-1.21 C-1.42 A-1.34 5.62 C-1.45
5.35 A-1.67 C-0.71 B-1.66 D-1.18 5.22 D-1.56 A-1.65 C-0.66 5.17 Totals 6.35 4.39 6.14 4.47 21.36 CF = [21.36]2/16 = TSS = [ … ] – CF =

19 Example Row/Col 1 2 3 4 Total B-1.64 D-1.21 C-1.42 A-1.34 5.62 C-1.45
5.35 A-1.67 C-0.71 B-1.66 D-1.18 5.22 D-1.56 A-1.65 C-0.66 5.17 Totals 6.35 4.39 6.14 4.47 21.36 Row SS = [ ]/4 – CF = Col SS = [ ]/4 – CF =

20 Error = Total SS – Row SS – Col SS – Gen SS
Example Row/Col 1 2 3 4 Total B-1.64 D-1.21 C-1.42 A-1.34 5.62 C-1.45 A-1.18 D-1.40 B-1.29 5.35 A-1.67 C-0.71 B-1.66 D-1.18 5.22 D-1.56 A-1.65 C-0.66 5.17 Totals 6.35 4.39 6.14 4.47 21.36 Gen SS = [ ]/4 – CF = Error = Total SS – Row SS – Col SS – Gen SS

21 * = 0.05 > P > 0.01; ** = 0.01 > P > 0.001
Analysis of Variance Source df SS MS F Rows 3 0.0301 0.0101 0.46 ns Column 0.8274 0.2758 12.78 ** Genotypes 0.4268 0.1423 6.69 * Error 6 0.1296 0.0216 Total 15 1.4139 * = 0.05 > P > 0.01; ** = 0.01 > P > 0.001

22 Efficiency of Latin Squares
cw CRB Design [MSr + MSc + (t-1)EMS]/(t+1)EMS [ (4-1)0.0216/(4+1)0.0216 = 3.25 Latin square in this instance increased precision by 225% over CRB CRD would have need 2.25 x 4 = 9 replicates to be as accurate.

23 Efficiency of Latin Squares
cw RCB Design R(RCB) = [MSr + (t-1)EMS]/(t+1)EMS C(RCB) = [MSc + (t-1)EMS]/(t+1)EMS R(RCB) = 0.81 : C(RCB) = 3.66 Latin square in this instance increased precision on 266% over RCB or is less precise if replicates were switched.

24 a. I II III IV I II b. III IV I III c. II IV

25 +266% -19%

26 Analyses of Lattice Squares
Yijk =  + ri + baj + tak + eijk See Table 5 & 6, Page 105 & 106

27 Analyses of Lattice Squares
Calculate sub-block totals (b) and replicate totals (R). Calculate the treatment totals (T) and the grand total (G). For each treatment, calculate the Bt values which is the sum of all block totals that contain the ith treatment.

28 Analyses of Lattice Squares
Calculate sub-block totals (b) and replicate totals (R). Calculate the treatment totals (T) and the grand total (G). For each treatment, calculate the Bt values which is the sum of all block totals that contain the ith treatment.

29 Analyses of Lattice Squares
Treatment 5 is in block 2, 5, 10, 15, and 20, so B5 = = 3411. Note that the sum of the Bt values is G x k, where k is the block size. For each treatment calculate: W = kT – (k+1)Bt + G W5 = 4(816)-(5)(3,411)+13,746 = -45

30 Lattice Square ANOVA - d.f.
Source df Reps k 4 Trt(unadj) k2 – 1 15 Block(adj) Intra-Block Error (k-1)(k2-1) 45 Trt (adj) k2 – 1 Effective Error Total k2(k+1)-1 79

31 Analyses of Lattice Squares
Compute the total correction factor as: CF = (∑xij)2/n CF = G2/[(k2)(k+1)] (13,746)2/(16)(5) 2,361,906

32 Analyses of Lattice Squares
Compute the total SS as: Total SS = xij2 – CF [ …+2252] – 2,361,906 = 58,856

33 Analyses of Lattice Squares
Compute the replicate block SS as: Replicate SS = R2/k2 – CF [ …+29252]/16 – 2,361,906 = 5,946

34 Analyses of Lattice Squares
Compute the unadjusted treatment SS as: Treatment (unadj) SS = T2/(k+1)–CF [ …+8662]/5 – 2,361,906 = 26,995

35 Analyses of Lattice Squares
Compute the adjusted block SS as: Block (adj) SS = W2/k3(k+1) – CF [ …+8662]/320 – 2,361,906 = 11,382

36 Analyses of Lattice Squares
Compute the intra-block error SS as: IB error SS = TSS–Rep SS–Treat(unadj) SS–Blk(adj) SS 58, , , ,382 = 14,533

37 Lattice Square ANOVA Calculate Mean Squares for block(adj) and IBE.
Source df SS MS Reps 4 5,946 1,486 T(unadj) 15 26,995 1,800 Blk(adj) 11,382 759 Intra block error 45 14,533 323

38 Analyses of Lattice Squares
Compute adjusted treatment totals (T’) as: T’i = Ti + Wi  = [Blk(adj) MS-IBE MS]/[k2 Blk(adj) MS]

39 Analyses of Lattice Squares
Compute adjusted treatment totals (T’) as:  = [ ]/(16)(759) = T’ = T + W  = [Blk(adj) MS-IBE MS]/[k2 Blk(adj) MS]

40 Analyses of Lattice Squares
Compute adjusted treatment totals (T’) as: Note if IBE MS > Blk(adj) MS, then =zero. So no adjustment. T’ = T + W  = [Blk(adj) MS-IBE MS]/[k2 Blk(adj) MS]

41 Analyses of Lattice Squares
Compute adjusted treatment totals (T’) as: Note also greatest adjustment when Blk(adj) MS large and IBE MS is small. T’ = T + W  = [Blk(adj) MS-IBE MS]/[k2 Blk(adj) MS]

42 Analyses of Lattice Squares
Compute adjusted treatment totals (T’) as: T’5 = T5 + W5 T’5 = x (-45) = 814 T’ = T + W  = [Blk(adj) MS-IBE MS]/[k2 Blk(adj) MS]

43 Analyses of Lattice Squares
Compute adjusted treatment means (M’) as: M’ = T’/[k+1]

44 Analyses of Lattice Squares
Compute adjusted treatment SS as: Treat (adj) SS = T’2/(k+1) – CF [ …+8392]/5 – 2,361,906 = 24,030

45 Analyses of Lattice Squares
Compute effective error MS as: EE MS = (Intra-block error MS)(1+k) 323[1 + 4(0.0359)] 369

46 Lattice Square ANOVA Source df SS MS F Reps 4 5,946 T(unadj) 15 26,995
Blk(adj) 11,382 Intra error 45 14,533 T(adj) 24,030 Eff. Error 16,605

47 Lattice Square ANOVA Source df SS MS F Reps 4 5,946 1,486 4.03 *
T(unadj) 15 26,995 1,800 - Blk(adj) 11,382 759 2.35 ns Intra error 45 14,533 323 T(adj) 24,030 1,602 4.34 ** Eff. Error 16,605 369

48 Efficiency of Lattice Design
100 x [Blk(adj)SS+Intra error SS]/k(k2-1)EMS 100 [11, ,533]/4(16)369 117% I II III IV V I II III IV V

49 Lattice Square ANOVA Source df SS MS F Reps 4 5,946 1,486 4.03 *
T(unadj) 15 26,995 1,800 - Blk(adj) 11,382 759 2.35 ns Intra error 45 14,533 323 T(adj) 24,030 1,602 4.34 ** Eff. Error 16,605 369

50 RCB ANOVA Source df SS MS F Reps 4 5,946 1,486 3.44 * T(unadj) 15
26,995 1,800 4.25 ** Error 60 25,915 432 -

51 Lattice Square ANOVA Source df SS MS F Reps 4 5,946 1,486 4.03 *
T(unadj) 15 26,995 1,800 - Blk(adj) 1,382 92 0.17 ns Intra error 45 24,533 545 T(adj) 24,030 1,602 2.71 * Eff. Error 26,605 591

52 Lattice Square ANOVA CV Lattice = 11.2%; CV RCB = 12.1%.
Range Lattice 119 to 197; Range RCB 116 to 199. Variation between treatments is small compared to environmental error or variation.

53 Comparison of Rankings

54 ANOVA of Factorial Designs


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