In the test of a contingency table,the observed cell frequencies must satisfy the rule of 5.

The rule of 5 states that in a contingency table, every expected cell frequency must be at least 5 in order to use the chi-square test for independence. There is no requirement on the observed cell frequencies. However, if any of the expected cell frequencies are less than 5, then the chi-square test may not be valid and other methods of analysis should be considered.