Question 1143688
.
A student doing an internship at a large research firm collected the following data, representing all of the studies 
the firm had conducted over the past 3 years.
 
What is the probability that the study did not use randomization, if we already know that the study was 
a retrospective observational study?
 
<pre> 
Randomization?	Retrospective Observational	Prospective Observational	Experiment	Total
Yes	         7	                        28	                         35	          70
No	        53	                        62	                        115	         230
Total	        60	                        90	                        150	         300

	
<U>Answer options</U>
0.88
	
0.85
	
0.27
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&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;What you see above -- is your post.


&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Please pay attention on &nbsp;&nbsp;<U>how &nbsp;I &nbsp;EDITED &nbsp;(formatted) &nbsp;it</U> &nbsp;&nbsp;<U>TO &nbsp;MAKE &nbsp;SENSE</U>.



<pre>
<U>ANSWER</U>.    P = {{{53/60}}} = 0.88  (correct with 2 decimal places)


Although the formula is SELF-EXPLANATORY, I will give some <U>explanation</U>.


    Go to the column "Retrospective Observational", take there two appropriate numbers "53" and "60" and make a ratio.
</pre>