Quasi Experimental Studies

Quasi experimental designs are based on the same structure as experimental designs but lack the randomization, control, or both. These designs are often used in field research settings with intact groups.

This design lacks:
a.    Either randomization
b.    Comparison group
c.    Or both

In this, subjects are members of intact group or divided on the basis of attribute variables into groups of subjects, where subjects are used as their own control.

Advantages

They are appropriate when stronger designs are not feasible

Uses

a.    Field research
b.    Education
c.    Social science research

http://howmed.net/community-medicine/quasi-experimental-studies/