Question 93698
1) For the grouped data: 

Score Frequency 
90-100 8 
80-89 12 
70-79 26 
60-69 14 

An estimate of the mean is _____ 

Use the "mark" of each class as a representative value; multiply each
mark by its corresponding frequency; add the results; divide by the 
sum of the frequencies to get the estimate of the mean:
8*95 + 12*84.5 + 26*74.5 + 14*64.5 = 4614
4614/60 = 76.9
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2)The expected value of the following probability distribution is ___________. 

xi 1      5   10   20   50 
pi 0.30 0.40 0.10 0.15 0.05
Multiply each xi by its corresponding pi and add the results to get the expected value:
1*.3 + 5*.4 + 10*.1 + 20*.15 +50*.05 = 8.8
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3) Of 200 students surveyed 40 subscribe to Time Magazine, 65 subscribe to Sports Illustrated, and 10 subscribe to both. If a student is selected at random, what is the probability the student subscribes to Time Magazine or Sports Illustrated?
P(T or S) = P(T) + P(S) - P(T and S)
= (40/200) + (65/200) - (10/200)
= 95/200
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4) A consumer's group checked the gasoline mileage (to the nearest mile per gallon) on 25 different cars. The following gives a summary of the findings. 

Miles per Gallon Frequency 
Less than 15....... 2 
16-20 ..............4 
21-30 .............13 
31-40 ..............5 
Over 40 ............1 

What quantities can be obtained from the table? 
An estimate of the mean; estimate of standard deviation; estimate of mode;
estimate of median; estimate of range; estimate of minimum; est. of maximum.
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Cheers,
Stan H.