Q.34
In an experiment, the experimenter observes proportion of individuals affected by a disease in each of the plots by examining
a random sample of individuals within each piot. If p is the observed proportion, then the appropriate variance stabilizing
transformation in this case will be
EXPLANATION
Probability Theory, Random Variables, Expectation, Generating Functions & Probability Distributions
- Variance Stabilizing Transformations:
- When analyzing proportional data ($p$) where observations follow a binomial distribution, the variance is proportional to $p(1 - p)$, which depends heavily on the mean.
- Angular / Arcsine Transformation:
- The variance-stabilizing transformation for binomial proportions or percentages is the sine inverse transformation ($f(p) = \arcsin(\sqrt{p})$ or $\sin^{-1}\sqrt{p}$).
- This stabilizes the variance to a constant value of approximately $\frac{1}{4n}$ (in radians), satisfying the homoscedasticity assumption of ANOVA.
- Other Transformations:
- Square root transformation ($\sqrt{x}$ or $\sqrt{x + 0.5}$): Used for count data following a Poisson distribution.
- Logarithmic transformation ($\log x$): Used when standard deviation is proportional to the mean.
- Fisher's $z$-transformation: Used to normalize the sample correlation coefficient $r$.
- Conclusion: The appropriate transformation is Sine inverse transformation (Option 2).
Correct option: (2) Sine inverse transformation
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