Answer:
option (c) 47.5%
Explanation:
Given:
Mean score into a math class, μ = 80
Standard deviation, σ = 10
Prescribed range between 60 and 80
Range in 1 standard deviation from mean
μ ± σ
i.e
80 - ( 1 × 10 ) and 80 + ( 1 × 10 )
or
70 and 90
our prescribed range of 60 and 80 does not lies in the obtained range
thus,
Range in 2 standard deviation from mean
μ ± σ
i.e
80 - ( 2 × 10 ) and 80 + ( 2 × 10 )
or
60 and 100
our prescribed range of 60 and 80 lies in the obtained range i.e within 2 standard deviations of the mean.
therefore,
The interval is half of that because it is the data between the mean and two standard deviations below the mean.
Hence,
= 47.5%
Hence,
The correct answer is option (c) 47.5%