To standardize the values, you need to subtract the mean and divide the result by the standard deviation.
... z = (x - μ)/σ
The mean, of course, is the sum of values divided by 7. The standard deviation is the square root of the quantity the mean of the squares minus the square of the mean.
μx = 212.10/7 = 30.30
σx = √(6427.7236/7 -30.30²) ≈ 0.3953
μy = 17.81/7 ≈ 2.5443
σy = √(45.4205/7 - 2.5443²) ≈ 0.1235
It is convenient to let a calculator or spreadsheet do these repetitive calculations. The attached table shows the zx, zy, and zxzy. The table uses t and g in place of x and y.
