Formula to find mean and standard deviation is,
Means = np and standard deviation =.
Where n= sample size, p = probability.
According to the given problem, the probability that an individual has 20 vision is 0.19 in a class of 70 students. So,
p = 0.19 and n = 70.
Hence, the first step is to plug in these values in the above formula to get mean and standard deviation. Therefore,
Mean = np
= 70* 0.19
= 13.3
= 13.300 (Rounded to nearest thousandth.
Standard deviation =
=
=
=√10.773
=3.282224855
= 3.282 (Rounded to nearest thousandth).