Calculating the expected value of SSTr

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Hei,

I was trying to calculate the expected value of Treatment sum of squares and I saw this ...

$$E(\text{SSTr})=(I-1)\sigma^2+J\left(\sum_{I}{(\mu_i^2-\mu^2)}\right) = (I-1) \sigma^2+J\left(\sum_I (\mu_i-\mu)\right)=$$

My question is is this correct and how to prove that(I tried to come from righ to left but it didnt work out)

$$\sum_I (\mu_i^2-\mu^2) = \sum_I(\mu_i-\mu)^2$$

$I$ : is number of treatments

$\mu$: is the total expected value

$\mu_i$: the expected value of each treatment

$J$: number of observations

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$$\sum_{i=1}^{n}(\mu_i-\mu)^2=\sum_{i=1}^{n}(\mu_i^2-2\mu_i\mu+\mu^2)=\sum_{i=1}^{n}(\mu_i^2+\mu^2)-2\mu\sum_{i=i}^{n}\mu_i=\sum_{i=1}^{n}(\mu_i^2+\mu^2)-2n\mu*\mu$$

$$\sum_{i=1}^{n=1}(\mu_i^2+\mu^2)-2n\mu^2=\sum_{i=1}^{n}(\mu_i^2+\mu^2) -\sum_{i=1}^{n}2\mu^2=\sum_{i=1}^{n}(\mu_i^2+\mu^2-2\mu^2)=\sum_{i=1}^{n}(\mu_i^2-\mu^2)$$

$$\mathcal{Q.E.D}$$

Hope this is helpful.