Answer :
In standard deviation, 120 is the percentile of this class.
Why is there a standard deviation?
- The term "standard deviation" (or "") refers to the degree of dispersion of the data from the mean.
- Data are grouped around the mean when the standard deviation is low, and are more dispersed when the standard deviation is high.
Test statistic (z) = (weekly study time - average study time)/standard deviation
weekly study time = 2.3 hours
average study time = .5 hours
standard deviation = 1.5 hours
z = (2.3 - 0.5)/1.5
= 1.8/1.5 = 1.2 (to 2 decimal places)
Cumulative area of the test statistic is 1.2
Percentile = 1.2×100 = 120
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