In: Statistics and Probability
Assume that you have a box of resistors that have a
Gaussian distribution of resistances with mean µ = 100 Ω and
standard deviation σ = 20 Ω
(i.e., 20% resistors). Suppose that you wish to form a subgroup of
resistors
with µ = 100 Ω and standard deviation 5 Ω (i.e., 5% resistors) by
selecting all resistors with resistance between the two limits r1 =
µ−a and r2 = µ+a.
(Apparently, you are too cheap to just order the resistors with the
appropri-
ate resistance tolerance from Mouser.)
(a) Find the value of a.
(b) What fraction of resistors should satisfy the condition?
(c) Find the standard deviation of the remaining sample.
Here 5% of the resistors mean we need to compute the confidence interval for the given parameters using normal distribution.
We assume that the n = 1000
Following are the calculations for the same,
Value of a = 0.31
b) Almost, 95% of the population will fall into this group
c) Std dev of the remaining sample = sigma/(0.05*n)