Mobile Phones Sales
After analyzing sales data,the owner of a Mobile Phone store produced the following joint probability distribution of the number of iPhones (X)and Blackberries (Y)sold daily. 
-{Mobile Phones Sales Narrative} Find the marginal probability distribution of the number of Blackberries sold daily.
Definitions:
Placebo
A substance or treatment which is designed to have no therapeutic value, commonly used as a control in testing new drugs.
Correlation Coefficient
A statistical measure that describes the degree to which two variables move in relation to each other, ranging from -1 to 1.
Perfect Correlation
A statistical relationship indicating a flawless direct or inverse linkage between two variables.
Matched Design
A research design that matches the experimental participants with control participants who are similar on key characteristics.
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