Tamara and Derek are sales associates in a large electronics and appliance store

Question

Tamara and Derek are sales associates in a large electronics and appliance store. Their store tracks each associate's daily sales in dollars Tamara's sales total varies from day to day with mean $1100 and standard deviation $100. Derek's sales total Y also vanes, with mean $1000 and standard deviation $80. Because the store is large and Tamara and Derek work m different departments, we might assume that their daily sales totals vary independently of each other. What are the mean and standard deviation of the total daily sales made by both Tamara and Derik, i.e. X+Y? What are the mean and standard deviation of the difference between Tamara s and Derek s daily sales, i.e. X-Y? Tamara sells more than Derek on the average Docs that mean she sells more every day? Why? Applying probability rules The game of Texas hold starts with each player receiving two cards. Here is the probability distribution for the number of aces in two-card hands:

Explanation / Answer

Result:

a).

mean of X+Y = 1100+1000 =2100

variance of X+Y = 100^2 +80^2 =16400

standard deviation of X+Y = sqrt(16400) =128.0625

b).

mean of X-Y = 1100-1000 =100

variance of X-Y = 100^2 +80^2 =16400

standard deviation of X-Y = sqrt(16400) =128.0625

c).

No, this does not mean she sells more every day.

2 sd limit for Tamara = (1000,1200) and 2 sd limit for Derek = (840,1160).

Lower limit of Tamara is less than the upper limit of Derek. This shows for some days, Tamara sells less than Derek.

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