What is the standard deviation of company r's earnings per month for this year? (1) the standard deviation of company r's earnings per month in the first half of this year was $2.3 million. (2) the standard deviation of company r's earnings per month in the second half of this year was $3.9 million. 2. what is the standard deviation of q, a set of consecutive integers? (1) q has 21 members. (2) the median value of set q is 20. 3. lifetime of all the batteries produced by certain companies have a distribution which is symmetric about mean m. if the distribution has a standard deviation of d , what percentage of distribution is greater than m+d? (1) 68 % of the distribution in the interval from m-d to m+d, inclusive (2) 16% of the distribution is less than m-d 4. question deleted 5. list s and list t each contain 5 positive integers, and for each list the average of the integers in the list is 40. if the integers 30,40 and 50 are in both lists , is the standard deviation of the integers in list s greater than the standard deviation of the integers in list t? (1)the integer 25 is in list s (2)the integer 45 is in list t 6. set t consists of odd integers divisible by 5. is standard deviation of t positive? (1) all members of t are positive (2) t consists of only one member 7. set x consists of 8 integers. is the standard deviation of set x equal to zero? (1) the range of set x is equal to 3 (2) the mean of set x is equal to 5 8. {x,y,z} if the first term in the data set above is 3, what is the third term? (1) the range of this data set is 0. (2) the standard deviation of this data set is 0. 9. question deleted 10. a scientist recorded the number of eggs in each of 10 birds' nests. what was the standard deviation of the numbers of eggs in the 10 nests? (1) the average (arithmetic mean) number of eggs for the 10 nests was 4. (2) each of the 10 nests contained the same number of eggs. 11. during an experiment, some water was removed from each of the 6 water tanks. if the standard deviation of the volumes of water in the tanks at the beginning of the experiment was 10 gallons, what was the standard deviation of the volumes of water in the tanks at the end of the experiment? (1) for each tank, 30% of the volume of water that was in the tank at the beginning of the experiment was removed during the experiment. (2) the average (arithmetic mean) volume of water in the tanks at the end of the experiment was 63 gallons. calculating standard deviation of a set {x1, x2, ... xn}: 1. find the mean, m, of the values. 2. for each value xi calculate its deviation (xi-m) from the mean. 3. calculate the squares of these deviations. 4. find the mean of the squared deviations. this quantity is the variance. 5. take the square root of the variance. the quantity is th sd. tips: 1. |median-mean| <= sd?