Chebyshev's inequality and SD of a combined list.
1) Suppose that a BART ride from Berkeley to San Francisco takes a mean time of 38 minutes with a standard deviation of 4 minutes. If you want to make the claim "At least 90% of BART rides from Berkeley to San Francisco take between _______ and _________ minutes", what numbers should be used to fill in the blanks?
2) A list of transactions contains 100 numbers: 60 gains and 40 losses. The gains are positive numbers and the the losses are negative numbers. The units are thousands of dollars. For the 60 gains, the average is 18 and the SD is 7.5. For the losses the average is -20 and the SD is 9.2.
a) Find the average of the 100 transactions (answ: avg=2.8)
b) Find the SD of the 100 transactions. (answ: SD=20.35)