Shian-Loong

I think they are very similar concepts that both develop from similar problems of considering a comparison of the 'rational' view to the discussion of how people actually make decisions.

The comparison and similarities are striking and we can list the similarities but what are the differences? That might be useful to think about.  

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 Effectuation theory of entrepreneurship was developed vy Professor Sarasvathy after exhaustively interviewing 27 serial entrepreneurs.  Her research findings greatly advanced the answer to the age-old-question – What do entrepreneurs actually do?

Effectuation is defined as a form of reasoning or problem solving which assumes that the future is largely unpredictable, but it can be controlled through human action.   This is in stark contrast to another form of reasoning, Causality, which assumes the future is theoretically predictable based on prior events.

Shian-Loong, if you're scoping this subject area, it's also worth looking at recent work on entrepreneurial 'bricolage', a somewhat related concept that tends to be more narrowly focused around the process of acquiring and configuring resources and capabilities - I'd suggest these for starters: Baker, Ted, and Reed E. Nelson. "Creating something from nothing: Resource construction through entrepreneurial bricolage." Administrative science quarterly 50.3 (2005): 329-366; Di Domenico, MariaLaura, Helen Haugh, and Paul Tracey. "Social bricolage: Theorizing social value creation in social enterprises." Entrepreneurship theory and practice 34.4 (2010): 681-703.

There is also a significant overlap with the literature on 'Onganisational Improvisation'.

you may want to look at the Moorman & Miner articles from 1998 and e Cunha et al from 1999, plus a whole pile of stuff that has been written since.  If you need the full references, let me know.  Richard is correct about the Bricolage linkage.  Bricolage is also a construct of Organisational Improvisation, hence the overlap. 

There also used to be an Effectuation group on LinkedIn (I am a member), but I am not sure how active it is.  It is an academic group, and the members are all interested in Effectuation in one way or another.

Entrepreneurship is a little outside my expertise, but in plain English, I consider "muddling through" to mean doing the minimum needed to accomplish a job, with no detailed plan and without an emphasis on quality.

This does NOT seem to be the same as Arun defined Effectuation.

Found this article interesting as to a contrast between effectuation and the evolutionary/Schumpeterian behavioral model of the entrepreneur:

https://www.researchgate.net/publication/225409925_Schumpeters_conduct_model_of_the_dynamic_entrepreneur_scope_and_distinctiveness._J_Evol_Econ

Article Schumpeter's 'conduct model of the dynamic entrepreneur': Sc...

My opinion is that they are different instead. The first one is rather rational, more problem-solving oriented, deterministic. The second one is based on the experimentation concept (try through mistakes).