Here we have :
Mean = 70
Standard deviation = 5
Interquartile range IQR = Q3 - Q1
where Q1 and Q3 are at 25th and 75th percentile.
for 25 and 75th percentile; z = -/+0.6745
25th percentile Q1 = mean +z*std deviation = 70-0.6745*5 = 66.628
75th percentile Q3 = mean +z*std deviation = 70+0.6745*5 = 73.372
hence,
IQR = Q3 - Q1 = 73.372 - 66.628 = 6.75
Correct option "E"
6.75
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