The correct order of basicity of amines in water is:

Basicity of amines increase with increase in number of – CH3 groups (or any group which cause +I effect), due to increase in electron density on N atom. As a rule, the basicity of t-amine should be more than that of s-amine, but actually it is found to be lesser than s-amines. This is due to stearic hindrance of bulkier alkyl groups, which decreases the availability of lone pair of electron on the N atom of the amino group. Hence the correct order of basicity is:CH32NH>CH33 N>CH3NH2