# Examples of Point Estimation of the Average Example 5.3

An engineer uses 100 samples to check the average noise output of amplifiers (in Db) produced in the production line. If it is known that the line is normally distributed with standard deviation of the noise measurements equal to 10, what is the maximum error (in dB) of the noise measurement population average given that the engineer wants to express it with a probability of 99%?

The engineer can state with 99% probability that error between the sample average and the population average is less then 2.575 dB.

Example 5.4

A factory makes PCBs and the gold plating thickness on the PCB fingers is expected to meet a minimum value of 20 mils prior to shipping. The gold thickness population is normal, with an average equal to 10 mils and standard deviation σ equal to 3.0. Process improvements were made to reduce variability, and hence less gold can be plated on average to ensure conformance to specifications. How many units must be made with the new process to ensure with 95% probability (a= 0.025) that new population average is within 土 1 mil?

### Example 5.5

A sample of nine measurements was taken for tum-on rise time of an IC. The average of the sample was 51 units and the sample standard deviation was 6, Given that this sample is derived from a population with normal distribution, calculate the maximum error of the population average with 95% confidence.

E is the maximum error between the sample average and the population average, with 95% confidence.