The frequency distribution summarizes a sample of time (in mins) between eruptions of a certain geyser. Find the standard deviation of the data. (ONLY ANSWER NEEDED, NO NEED TO SHOW WORKING)
Time Frequency
40-49 10
50-59 41
60-69 23
70-79 6
80-89 104
90-99 15
100-109 1
2007-10-24 06:08:07 · 2 answers · asked by austin 1 in Science & Mathematics ➔ Mathematics
Let xi be the mid-point of each interval and fi be the frequency of that interval.
Then finding the variance of grouped data is found by:
s² = [n∙Σxi²fi-(Σxifi)²]/(n(n-1)) = [200∙1158030-(14920)²]/39800
=8999600/39800 = 226.12
s = 15.04
2007-10-24 07:27:21 · answer #1 · answered by cvandy2 6 · 0⤊ 0⤋
Not enough information. You would need to know the exact times in each segment. I guess you could get an approximation by assuming that all results fall in the center of each segment (e.g. all in the 40-49 segment equal 44).
Using this method, I got a sigma of 15.04.
2007-10-24 06:15:29 · answer #2 · answered by gebobs 6 · 0⤊ 1⤋