Question 1101392: Find the standard deviation.
50, 48, 20, 70, 41, 31, 40, 81, 63
Find the mode or modes.
20, 34, 46, 34, 49, 34, 49
Find the percent of the total area under the standard normal curve between the given z-scores.
z = 0.07 and z = 2.45
Find the median.
5, 8, 17, 22, 30, 41, 49
a. 30
Answer by math_helper(2461)   (Show Source):
You can put this solution on YOUR website! To find the standard deviation, you first need the mean (average):
(50+48+20+70+41+31+40+81+63)/9 = 49.3333…
Next you need to subtract the mean from each of the individual numbers:
0.666667, -1.333333, -29.333333, 20.666667, -8.333333, -18.333333, -9.333333, 31.666667, 13.666667
Next you square each of these values:
0.444445, 1.777777, 860.444442, 427.111125, 69.444444, 336.111099, 87.111105, 1002.777799, 186.777787
Next you sum these up:
2972.000023
Now divide by the number of data points (9):
2972.000023 / 9 = 330.222225 (this number is called the "variance"  of the data, its a measure of how much the data varies)
Now take the square root of the variance:
Ans (a): the standard deviation  is 
** You are supposed to ask ONE question per post, so I will provide general guidance for the rest of your questions **
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(b) The "mode" of a dataset is the most commonly occurring value. If there are two values that are most-common, they are both modes ("bimodal") and if there are three values tie for most-common then it is "trimodal" and beyond that it is "multimodal". If no element appears more often than any other then there is no mode. You can apply this to the data to figure out the mode.
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(c) You need a z-table to figure this one out (google for z-table, look for a left z-table and right z-table to help you figure this out).
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(d) The median is the middle value, when the data values are listed in increasing (or decreasing) order. If there are an even number of data values, take the numerical average of the two "middle" values.
Note: 30 is NOT the proper median for 5, 8, 17, 22, 30, 41, 49.
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