Need statistics help to use a two-factor ANOVA to analyze these data and interpret your results.

Dec 5th, 2015
Anonymous
Category:
Accounting
Price: $50 USD

Question description

Harley (2003) examined effects on growth of the red algae Mazzaella parksii, which forms lawn-like growths in the intertidal region. He focused on two factors: (1) location and (2) herbivore abundance. The two locations were in areas along the shoreline below where this algae normally occurs (Low zone) and in areas along the shoreline where this algae does normally grows (Mid zone). For herbivore abundance, he had areas where limpets (Lottia species) were removed (Absent) and areas where limpets were not removed (Present). Harley then measured the area covered by Mazzaella (in cm2) for each replicate plot, and obtained the following data (NOTE: 0.5 has been added to each value to remove any zeroes from the data):

Height

Herbivores

Area

Height

Herbivores

Area

low

absent

88.46

mid

absent

0.50

low

absent

1188.02

mid

absent

622.54

low

absent

2178.41

mid

absent

2168.20

low

absent

276.96

mid

absent

0.50

low

absent

594.26

mid

absent

26.42

low

absent

1470.77

mid

absent

38.20

low

absent

1140.90

mid

absent

2204.33

low

absent

3732.72

mid

absent

524.36

low

absent

1257.14

mid

absent

377.49

low

absent

2132.08

mid

absent

1378.88

low

absent

1254.00

mid

absent

201.56

low

absent

627.25

mid

absent

9.92

low

absent

0.50

mid

absent

467.03

low

absent

1689.11

mid

absent

276.96

low

absent

1307.41

mid

absent

2073.96

low

absent

1746.44

mid

absent

2297.80

low

present

143.44

mid

present

0.50

low

present

209.42

mid

present

1037.23

low

present

0.50

mid

present

1230.44

low

present

64.12

mid

present

307.59

low

present

0.50

mid

present

38.98

low

present

0.50

mid

present

170.15

low

present

763.91

mid

present

657.09

low

present

1847.76

mid

present

1332.54

low

present

9.92

mid

present

1407.94

low

present

69.62

mid

present

2095.95

low

present

0.50

mid

present

401.05

low

present

16.99

mid

present

99.46

low

present

0.50

mid

present

7.57

low

present

1294.05

mid

present

1610.57

low

present

12.28

mid

present

1665.55

low

present

7.57

mid

present

2012.69

A)  Use a two-factor ANOVA to analyze these data and interpret your results. The data are not currently set up correctly for doing a two-factor ANOVA in Excel, so you will likely need to rearrange them!

B)  Test these data to see if (1) they are normally distributed and (2) the groups have equal variances.

C)  If either assumption is violated, perform a data transformation to best eliminate the problem (you may or may not be able to completely eliminate any violations!). Then perform a second two-factor ANOVA, this time using the transformed data. How do your F-values and P-values differ if you compare the results of the two ANOVAs?


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