Unformatted text preview: Student: Grady Silnonton Course: Math119: Elementary Statistics  Spring 2010  CRN: 49239
Instructor: Shawn Parvini  16 weeks Date: 2/18/10 Book: Triola: Elementary Statistics, 11e
Time: 1:50 PM The mean of electrical energy consumption amounts for a home during a twomonth period is 2851 kWh, and the
standard deviation is 488 kWh. Use the range rule of thumb to identify minimum and maximum "usua “ amounts of
electrical energy consumption. For one particular twomonth period, the power company recorded consumption of 1820
kWh. Is that amount unusual? Recall that if the standard deviation is known, it can be used to find rough estimates of the minimum and maximum
"usual" sample values by using the following equations. minimum "usual" value = (mean) — 2 X (standard deviation)
maximum "usual" value = (mean) + 2 X (standard deviation) As given in the problem statement, the mean is 2851 kWh and the standard deviation is 488 kWh. Use these values to
ﬁnd the minimum and maximum "usual" values. minimum “usual“ value = (mean) — 2 X (standard deviation)
= (2851) — 2 X (488)
= 1875 kWh maximum "usual" value = (mean) +2 X (standard deviation)
= (2851) +2 X (488)
= 3827 kWh Based on the results above, a typical twomonth period for this house would consume between 1875 kWh and 3827 kWh of electrical energy. If 1820 kWh falls within these limits, it would be considered usual. If 1820 kWh does not fall
within these limits, it would be considered unusual. Page 1 ...
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 Spring '10
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