The "focal" association between category $i$ of one nominal variable and category $j$ of the other one is expressed by the frequency residualresidual in the cell $ij$, as we know: $n_{ij}-E_{ij}$, where $E_{ij}$ is the expected count under no association hypothesis. If the residual is 0 then it means the frequency is what is expected when the two nominal variables are not associated. The larger the residual the greater is the global association due to the overrepresented combination $ij$ in the sample. The large negative residual equivalently says of the underrepresented combination. So, frequency residual is what you want.
Raw residuals are not suitable though, because they depend on the marginal totals and the overall total and the table size: the value is not standardized in any way. But SPSS can display you standardized residuals also called Pearson residualsPearson residuals. St. residual is the residual divided by an estimate of its standard deviation (equal to the sq. root of the expected value). St. residuals of a table have mean 0 and st. dev. 1; therefore, st. residual serves a z-value, like z-value in a distribution ofbecause a quantitative variable (actually, it is z incount comes from Poisson distribution, where variance = expected value). St. residuals are comparable between different tables of same size and the same total $N$.
$Std.res._{ij}=\frac{n_{ij}-E_{ij}}{\sqrt{E_{ij}}}$
Chi-square statistic of a contingency table is the sum of the squared ststd. residuals in it. Comparing ststd. residuals in a table and across same-volumed tables helps identify the particular cells that contribute most to the chi-square statistic. Std. residuals are comparable between different tables of same size and the same total $N$.
SPSS also displays adjusted residualsStd. residual in a cell follows normal (= adjusted standardized residuals)$\mathscr{N}(0,\le1)$ distribution. AdjSo one may declare this residual greater than 2 or 3 by absolute value as significant one, telling of over- or under-representedness in the cell. However, because of $\le1$ sampling variance, std. residual is not fully a z-score of the normal distribution, and basing the inference of significance on it is conservative.
We may further divide std. residual divided by an estimate of its standard error. Interesting that adj. residual is just equal, to obtain $\sqrt{N}r_{ij}$adjusted standardized residuals (= adjusted residuals), which SPSS also displays.
$Adj.res_{ij}=\frac{Std.res._{ij}}{\sqrt{(1-n_{i.}/N)(1-n_{.j}/N)}}$
where $N$ is the grand total$n_{i.}$ and $r_{ij}$ is$n_{.j}$ are the Pearson correlation (alias Phi correlation) between dummy variables corresponding tomarginal counts of the categories $i$row and $j$ of the two nominal variablescolumn. ThisNow adj. residual in a cell follows normal $r$$\mathscr{N}(0,1)$ distribution; it is exactly what you say you want to computea true z-score. AdjIf adj. residual is directly related toabove 1.96 or below -1.96 you may conclude it is significant at p<0.05
level$^1$. 2.58 or -2.58 - for p<0.01
conclusion.
Unlike ststd. residual, adj. residual isappear also standardized wrt to the shape of the marginal distributions in the table (it takes into consideration the expected frequency not only in that cell but also in the cells outside its row and its column) and so you can directly see the strength of the tie between categories $i$ and $j$ - without worrying about whether their marginal totals are big or small relative the other categories' marginals. Adj
Interesting, that adj. residual is also like a z-scorejust equal to $\sqrt{N}r_{ij}$, but now itwhere $r_{ij}$ is like z of normalthe Pearson correlation (not Poissonalias Phi correlation) distributionbetween dummy variables corresponding to the categories $i$ and $j$ of the two nominal variables. If adjThis $r$ is exactly what you say you want to compute. Adj. residual is above 2 or below -2 you may concludedirectly related to it is significant at p<0.05
level$^1$. Adj. residuals are still effected by $N$; $r$'s are not, but you can obtain all the $r$s from adj. residuals, following the abovejust said formula, without spending time to produce dummy variables.$^2$
$^2$ It follows that the significance of the adjusted residual in cell $ij$ equals the significance of $r_{ij}$. Besides, if there is only 2 columns in the table and you are performing z-test of proportions between $\text {Pr}(i,1)$$\text {prop}(i,1)$ and $\text {Pr}(i,2)$$\text {prop}(i,2)$, column proportions for row $i$, the p-value of that test equals the significance of both (any) adj. residuals in row $i$ of the 2-column table.